#precalculus

1 messages · Page 286 of 1

vale urchin
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when you mix the two

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x(2) y(7)

winter quartz
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Our point should be (2,7)

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But we know every second we move down 4 and right 1

vale urchin
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yes

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so next point is 3, 3

winter quartz
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You got it

vale urchin
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Good wow okay

winter quartz
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And now this pattern is the same, so we have a line

vale urchin
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and that line is slowly curving to the right and rapidly moving down

winter quartz
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So it will look like that

vale urchin
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but it never stops?

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it doesnt curve?

winter quartz
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No, the pattern is the same through out

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This is a linear function

vale urchin
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oh just linear okay

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cool then

winter quartz
vale urchin
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oh okay cool good

obsidian monolithBOT
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dackid

winter quartz
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There we go

vale urchin
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yep okay infinite

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and you did a triangle

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so it cant change into a different triangle

winter quartz
vale urchin
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cant curve a triangle

winter quartz
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It let me know how much we were moving up and down

vale urchin
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it was greatly needed

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haha

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moving down 4

winter quartz
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But the red line is our actual graph

vale urchin
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okay so whats the big deal about parametric equations if theyre just linear?

winter quartz
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No no no my friend

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this parametric equation was linear

vale urchin
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oh

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oh dear okay

winter quartz
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Let's try a different one. Let's see what you can gather from it.

vale urchin
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also why is subscript 0 a thing

winter quartz
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$x(t)=t^2$
$y(t)=t^3$

obsidian monolithBOT
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dackid

winter quartz
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Try to graph that with just the tools we have

vale urchin
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okay so sqrt(x)=t

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y=cubroot(x)

winter quartz
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We'll let $0\leq t\leq 2$

obsidian monolithBOT
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dackid

vale urchin
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so I draw y = cuberoot(x)

winter quartz
vale urchin
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okay I'll try

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so goes up by squareroot

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so if t is 1

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then x is x^4

winter quartz
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No no. It goes up by t^3

vale urchin
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I mean to right sorry

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starting with x

winter quartz
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For $x(t)=t^2, x(1)=4$!?

obsidian monolithBOT
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dackid

winter quartz
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I call lies

vale urchin
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no its ^4?

winter quartz
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Well, technically right, but just because x(1)=1

vale urchin
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but if was 2

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2^6?

winter quartz
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-_-

vale urchin
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or 2^2

winter quartz
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If $x(t)=t^2$ what is x equal to when t=1?

obsidian monolithBOT
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dackid

vale urchin
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just 1^2

winter quartz
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Which is?

vale urchin
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1

winter quartz
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Yes

vale urchin
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so 2^2 is 4

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so when t = 2

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that is

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2^2 4

winter quartz
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For x(t), yes

vale urchin
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so y(t) = 1^3 is also 1

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but 2 is 2^3

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9

winter quartz
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Let's actually do from $-1\leq t\leq 2$

obsidian monolithBOT
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dackid

winter quartz
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3 is gonna be massive

vale urchin
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oh okay

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3 ^3

winter quartz
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Ooo, this is actually really interesting

vale urchin
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27

winter quartz
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Let's actually do $-2\leq t\leq 2$

obsidian monolithBOT
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dackid

vale urchin
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okay is that better?

winter quartz
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There is something really interesting going on in this interval

vale urchin
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its going up and to the right a lot

winter quartz
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Like I said, focus our t values on the interval above now

vale urchin
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can be -2 or 2

winter quartz
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t can be between -2 and 2

vale urchin
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but nothing lower or higher

winter quartz
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So check (x(t),y(t)) when t=-2,-1,0,1,2

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That will give you a good idea fo what will happen

vale urchin
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it will be the same as when -2 and 2 it is the same

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because squaring removes negative

winter quartz
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Ah, x will. But what about y?

vale urchin
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y no

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y is negative

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sometimes

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every other

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it is

winter quartz
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Your graph will end up looking something like this

vale urchin
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wow thats a new one

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so it repels

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and bends away

winter quartz
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I like that description. Pretty much 😁

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But something that may seem strange is it is symmetric across the x-axis

vale urchin
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whats that

winter quartz
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Do you know what the x-axis is?

vale urchin
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yes haha

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the horizontal

winter quartz
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So if you look at the horizontal line. The top looks like it is a mirrored version of the bottom

vale urchin
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oh thats what you meant

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my terminology is bad

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yes mirror makes sense

winter quartz
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But one of the first things you learn in algebra 1 and 2 is the vertical line test

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If you draw a vertical line anywhere, and two points on the graph are on the line, then it's not a function

vale urchin
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but center can be 0,0 though?

winter quartz
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I mean, that's not really relevant for the vertical line test

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The problem is two points on the graph hit the red line

vale urchin
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yes

winter quartz
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So, technically... this isn't a function

vale urchin
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you tricked me all along!

winter quartz
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But it is a parametric function weSmart

vale urchin
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😦

winter quartz
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Parametric functions allow you to represent any curve as a collection of functions over time. So any curve you draw on a graph, function or not, can be parametrized!

vale urchin
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so no more graphs then?

winter quartz
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No one said that

vale urchin
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Okay now im shook

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should I put the question now?

winter quartz
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Sure

vale urchin
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should I start by drawing and labeling the diagram below

winter quartz
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Well, A is given to be 40°

vale urchin
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So theta is given

winter quartz
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Yep, and so is v

vale urchin
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why do they give meters when we have feet for answer?

winter quartz
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The building is 63 ft high, so y_0=63 and x_0=0

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Everything needed is in ft

vale urchin
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we have speed

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32ft/s

winter quartz
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No no, gravity is $32 \frac{ft}{s^2}$

obsidian monolithBOT
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dackid

winter quartz
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And speed is $14\frac{ft}{s}$

obsidian monolithBOT
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dackid

vale urchin
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oh

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unfortunate

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y looks harder so lets start with x?

winter quartz
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Read the problem. Everything we need is given to us

vale urchin
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14 is initial speed

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which is v

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I get 10.7246222t + x_0

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for x(t)

winter quartz
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X_0=0

vale urchin
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10.7246222t just this yes

winter quartz
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If that's what it comes out to, yeah

vale urchin
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okay good good

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now y

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is tough

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but g is gravity?

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t^2 we need to get rid of the square somehow

winter quartz
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No we don't

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This is a function of t

vale urchin
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-1/2gt^2 + 8.999026536t + 63

winter quartz
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Also, just gonna say it right now, never plug numbers in until you are at the final stage

vale urchin
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oh

winter quartz
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And I can guarantee you 14sin(40) os perfectly acceptable for this program

vale urchin
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okay I do that then

winter quartz
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It is also more accurate than your approximation, as yours is just an approximation

vale urchin
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oh

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-1/2gt^2 + 14sin(40)t + 63

winter quartz
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And g is a number

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After that, yes. That's all you need

vale urchin
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g us 32

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is

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so -16

winter quartz
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Yep

vale urchin
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-16t^2 + 14sin(40)t + 63

winter quartz
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$y(t)=-16t^2+14\sin(40°)t+63$

obsidian monolithBOT
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dackid

vale urchin
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and no approximation

winter quartz
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Nope. This answer is as exact as it gets

vale urchin
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wow thats fire

winter quartz
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So now we now how high the canteloupe will be for any time t, and how far away it will be for any time t.

vale urchin
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So that has real world connection

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well thanks for the carry!

winter quartz
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You bet. Parametrized functions are simply a way to measure things with respect to time.

rose vapor
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$f_y$ where f(x,y) means what exactly? $df(x,y) \over dy$?

obsidian monolithBOT
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Daemon

winter quartz
obsidian monolithBOT
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dackid

rose vapor
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aaaaah

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damn it. I need to get better at latex

winter quartz
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No worries. I just wanted to make that clarification

rose vapor
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$\frac{d}{dx} [f(x,y)\frac {y'}{\sqrt{1+y'^{2}}}]$

winter quartz
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Essentially what you're doing is looking at a slice of the surface in the y-z plane and seeing what the derivative of f is with respect to y.

obsidian monolithBOT
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Daemon

winter quartz
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So say we have this amazingly drawn surface by yours truly

rose vapor
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haha. I think I got it :) So $f_y$ is taking a slice of f(x,y) and find it's tangent on the y-axis?

obsidian monolithBOT
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Daemon

rose vapor
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the above derivative is more calculus though right? :S

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oooh. right. you're doing it on xyz axis!

winter quartz
rose vapor
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or that :P

winter quartz
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So when you are taking a slice of the graph, you are looking at the y-z plane where x is a fixed number

rose vapor
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cooool :D

winter quartz
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Does that idea make sense?

rose vapor
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yeap

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it's hilarious that I'm doing an MSc on applied math and I'm excited when I understand these things XD

winter quartz
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Here is a quick example
Let $f(x, y)=xy$. Then $\frac{\partial f}{\partial y}=x$, since x is considered a constant

obsidian monolithBOT
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dackid

rose vapor
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and $\frac{\partial{f}}{\partial{x}} = y$

winter quartz
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Almost had it 😆

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But yes

obsidian monolithBOT
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Daemon

rose vapor
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ha!

winter quartz
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There ya go

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Also, some shorthand notation for that same thing is $f_y$ if it's a y partial and $f_x$ if it's an x partial.

obsidian monolithBOT
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dackid

winter quartz
rose vapor
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I thought it was precalculus :S

winter quartz
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Oh goodness no. This is multivariable calculus

rose vapor
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And this is? $\frac{d}{dx} [f(x,y)\frac {y'}{\sqrt{1+y'^{2}}}]$

obsidian monolithBOT
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Daemon

rose vapor
winter quartz
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Again, you are taking a partial here.

rose vapor
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wait...

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It's part of the euler-lagrange equation. It's written as d/dx. No θ/θx :\

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Gahhh. I'm calling it a night... WIll think again on it tomorrow.Many thanks for the help dackid :))

winter quartz
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Okay. Ask these questions in #calculus next time. This is definitely not pre calc.

rose vapor
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aye aye o7

vale urchin
vale urchin
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<@&286206848099549185>

lilac storm
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so i have solved this question but i just want to make sure that i did it right

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so first i started off by listing out all the things that are given which are, A=58750, r=0.05 and t=4

vale urchin
lilac storm
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then i used the A=Pe^rt formula and plugged everything in and rearranged the eq accordingly to find P and the answer i get is 48100.43 or simply 48100, i just want to ask that did i do everything correctly?

vale urchin
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Looks good to me

lilac storm
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so the formula is correct and just want to make sure just in case that 58750 is the A value (the future value) right?

vale urchin
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The formula is correct but did you plug in the right numbers?

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58750 is the A value yes

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thats your start

lilac storm
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ok, thank you so much for your help

vale urchin
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np

vale urchin
winter quartz
vale urchin
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then 18.70283481(86)

vale urchin
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😮

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well

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okay then

winter quartz
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I didn't say when solve y(t) when t=0, I said solve for t when y(t)=0

vale urchin
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ahhhh

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its that diagram thing you should me again

winter quartz
winter quartz
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Also, for approximations, you probably only need to round to the first two decimals

vale urchin
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so y(t) equals 0 it will be -4.9 + 18.06.... + 86

vale urchin
winter quartz
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$h(t)=0=-4.9t^2+18.06t+85$
Solve for t

obsidian monolithBOT
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dackid

vale urchin
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oh so first sqreroot both sides?

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get rid of ^2?

winter quartz
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Well, this is a quadratic equation

vale urchin
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oh so factor

winter quartz
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Time for the Quadratic Formula!!!!

vale urchin
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sadness

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I get two answers

winter quartz
vale urchin
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x = 6.39747242, -2.71153005

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one is ! lets gfoooo

winter quartz
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A negative time does not have any meaning

vale urchin
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so pick the positive

winter quartz
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So you only care when t is positive

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Correct

vale urchin
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yes!

winter quartz
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Now plug in that t in to x(t)

vale urchin
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oh okay will do

winter quartz
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After all, you're trying to show how far it traveled when it hit the ground. Well, it hit the ground at the time when y(t)=0

vale urchin
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119.650869873

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meter

winter quartz
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I mean sure. I'm not plugging it in

vale urchin
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Okay thanks for the carry

vale urchin
winter quartz
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I asked for it 😆

vale urchin
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and you deserve it haha

winter quartz
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Thanks, that's very kind of you :)

pastel carbon
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,w x^4-2x^2-24=0

obsidian monolithBOT
golden needle
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Can someone help me with my hw?

wispy aurora
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Yes, but post it

golden needle
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@wispy aurora

wispy aurora
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Why ping?

golden needle
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You said to post it earlier

wispy aurora
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Hm well ask someone else ig, rip

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Im tired

golden needle
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Ok

faint nest
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How do u do the second

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Ignore my graph idk what i’m doing lol

thorn moat
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x=log7^8-5/2, what does it mean to have log present after you have solved for the unknown? im having trouble understanding what a log truly is. i know that its used to find the unknown exponent but why keep log present once we have solved for x?

stable yacht
# faint nest How do u do the second

You know that from a half rotation, the height of the stone goes from 3 (the maximum height) to 0 (the minimum height). You need to figure out at which height the stone starts to model your graph. You know the span of one period since 0.4 seconds is one revolution.

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I’d fix the graph first and see if you can determine what equation to use after that.

wispy aurora
bold lintel
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I'm sure this is pretty simple and I'm just missing something here but everything I've thought of to solve for t would just contradict eachother when getting ln to the other side

jolly raven
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they isolated t by taking just the 4 and the ln

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because its like 4 times t times ln

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so they just divided 4 and ln to leave the t out

blissful hatch
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hi guys anyone know how to do question b? realshit

uncut mulch
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quotient + chain rule

blissful hatch
sick steppe
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yes, cause f is a quotient of functions

blissful hatch
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but how do i get the g function? it's not 2gx right?

sick steppe
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you're given enough information about g

uncut mulch
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differentiate g(x^2) using chain rule

blissful hatch
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okayy i got it thanksssssss

sick steppe
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Do what Ramonov said

still quarry
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anyone know where i went wrong here

sick steppe
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f is increasing on (1,inf) @still quarry

still quarry
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i see

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thanks

thorn moat
shrewd storm
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in its derivative

tender lotus
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what can't x be?

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not sure how to find that

sick steppe
tender lotus
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obviously not lol but i tried 0 and its wrong

sick steppe
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well when is x+5 = 0?

tender lotus
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-5, there we go, now it makes sense thanks

thorn moat
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How can i prove this to be true long hand with out a calculator? i am not sure i truly understand logarithms.

lethal oracle
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@thorn moat look up logarithm rules

wooden garnet
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Any ideas on how to do this

sterile wedge
#

Can someone please help me with the 2 I have circled? I don't know how to transform them based off of D and C and I also don't understand how to know where to put the line of the graph through

tranquil bronze
tranquil bronze
sterile wedge
tranquil bronze
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I was going to write a lot here, but there are so many videos on YouTube. I will refer you to one. I don't know if I can post the link here, so, check your pm.

lost mesa
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do lim x-> 0- and 0+ exist

sick steppe
lost mesa
sick steppe
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yes they both equal 0

lost mesa
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kk

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so therefore lim x->0 f(x) = 0 is true

sick steppe
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yes

lost mesa
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kk ty

sick steppe
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but f(x) is not continuous at x=0

lost mesa
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right

arctic walrus
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How do you simplify that?!

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How did they go from left to right

rustic glacier
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I'm not really sure but I tried it and I just multiplied both sides by 4 and got that it was equal

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so probably factor out 1/4

arctic walrus
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0oh no

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there's no both sides sorry

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They simplified from left to right

rustic glacier
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also in polar equations of conics is p directed distance or absolute value

arctic walrus
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Original problem for context/.

rustic glacier
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i'm getting the same answer as them but (sqrt 3 -1) in parentheses

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I just factored out 1/4 then -sqrt 2

arctic walrus
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i dont get it at all

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im sorry :/

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could you show your work?

rustic glacier
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@arctic walrus

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top part I just forgot to factor out negatives properly

arctic walrus
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wow dude thank you so much. So odd that that isn't taught in my book or by the teacher yet is expected.

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could you also show me this one?

rustic glacier
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yeah that’s taught in algebra but expanded on in precalc

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uhh try it first by multiplying by 3/3

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step 2 to step 3 is just substituting tangent values

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and step 3 to 4 is expanding and multiplying by 3/3 which is 1 so it doesn’t change the value

rustic glacier
arctic walrus
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that gives a crazy answer though

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oh shit okay

jovial salmon
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i just need help with finding the start and end pt, for some reason I get the same number for both

dapper night
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Does anyone know how to solve this

sick steppe
dapper night
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what’s that

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I just got in calculus with no context and they randomly give this hw to me

sick steppe
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the limit in the question

dapper night
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Without telling me steps

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Watched videos but still stuck

sick steppe
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$f'(x)=\lim_{h\to 0}\frac{f(x+h)-f(x)}{h}$

obsidian monolithBOT
#

moshill1

dapper night
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👀

viscid thistle
sick steppe
dapper night
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If you want me to be completely honest, I have no idea

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They put me from algebra one, to calculus

sick steppe
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ok so plug in x+h in for x and that's f(x+h)

dapper night
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Cause they said I had talent or something

sick steppe
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$\lim_{h\to 0}\frac{f(x+h)-f(x)}{h}=\lim_{h\to 0}\frac{3(x+h)^2-5(x+h)-3x^2+5x}{h} \ =\lim_{h\to 0}\frac{3x^2+6xh+3h^2-5x-5h-3x^2+5x}{h}$

obsidian monolithBOT
#

moshill1

dapper night
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Do you cancel out 3x^2, -5x, -3x^2?

sick steppe
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after expanding the brackets stuff will cancel, yes

dapper night
#

This is what I got

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But I’m now stuck

sick steppe
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didnt distribute properly

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also forgetting the limit in every line

dapper night
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😞

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Would you mind taking me step by step?

past meadow
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lost some 3's while distributing

sick steppe
#

almost like that's what I was referring to

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$\lim_{h\to 0}\frac{f(x+h)-f(x)}{h}=\lim_{h\to 0}\frac{3(x+h)^2-5(x+h)-3x^2+5x}{h} \ =\lim_{h\to 0}\frac{3x^2+6xh+3h^2-5x-5h-3x^2+5x}{h} \ =\lim_{h\to 0}\frac{6xh+3h^2-5h}{h}$

dapper night
#

Hmmm

obsidian monolithBOT
#

moshill1

dapper night
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👀

winter quartz
#

Almost there :)

dapper night
#

I’m so stuck 😣

winter quartz
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Well, factor out an h from the top

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So $\lim_{h\to 0} \frac{h(6x+3h-5)}{h}$

obsidian monolithBOT
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dackid

dapper night
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Do you cancel h now?

winter quartz
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I don't see why not

dapper night
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6x + 3h - 5

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?

past meadow
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yeah, and as h approaches 0...

dapper night
#

6x-5?

winter quartz
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Bingo!

dapper night
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Thank y’all!

woven ravine
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hello,new here. i am really bad at these type of Qs where it asks of me to prove something is something, it would be really appreciated if someone could help me out a bit with the process

woven ravine
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<@&286206848099549185> apologies for the ping. This type of question really confuses me a lot

grave tartan
#

Basically

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It’s just a little analysis

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When something is symmetrical along y=x

woven ravine
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isn't it a straight line?

grave tartan
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You gotta ask Well how do we go about proving that

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Y=x is straight but also

woven ravine
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english not my 1st language,so I do apologize for my crappy eng lol

grave tartan
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What do we know is associated with y=x

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No worries

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Lmk if you want a hint

woven ravine
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tbh

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I don't understand this question almost at all

grave tartan
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Yeah so we know that inverses are reflected along y=x

woven ravine
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all i could kind of guess was since y=x symmetry, it would be a straight line

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yeah

grave tartan
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Well pull up desmos rq

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Plot y=x and y = 1/x

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Lmk when you have

woven ravine
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y=x is just a tilted line going straight through at a 45 degree

grave tartan
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Yeah but also

woven ravine
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and the y=1/x is an even function

grave tartan
#

If you flip the graph over the line y=x

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You get the same exact graph

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That’s what symmetrical means

woven ravine
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oh so it's a reciprocoal?

grave tartan
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One side is identical to the other

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It’s an inverse

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A special property of 1/x is that it is its own inverse

woven ravine
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is y=x

grave tartan
#

Basically the question is asking you to prove that expression is it’s own inverse

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Do you know how to find inverses?

woven ravine
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isn't it like

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you get the function

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then switch the y and x values

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to solve for f-1(x)

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I had to serve a mandatory military service and everything about math is jumbled into a mess in my head...

grave tartan
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Nah bro you’re good

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That’s exactly it

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You flip the x and y and solve for y again

#

Basically a neat thing about the function it gave is that it is it’s own inverse and the question is just asking you to prove that fact

winter quartz
#

Interestingly, that function is significantly linked to a 2x 2 matrix's determinant

#

Which I dunno, I find super interesting

woven ravine
#

I really appreciate the help guys, but I'd like to be a bit selfish and ask for just the first step in as to how to begin

#

so what I got down so far

winter quartz
#

Start here: $x=\frac{ay+b}{cy-a}$

#

And now try to solve for y

obsidian monolithBOT
#

dackid

woven ravine
#

oh god

#

my pea sized brain

winter quartz
woven ravine
#

i know we have to single out y

#

but i am not sure what number to multiply both sides by,in order to single out the fraction

winter quartz
#

Well, the number in the denominator

#

$\frac{a}{b}\cdot b=a\cdot\frac{b}{b}=a$

woven ravine
#

so then x(cy-a)=ay+b

obsidian monolithBOT
#

dackid

winter quartz
#

Quick algebraic reason as to why we do that

winter quartz
woven ravine
#

then...divide by a...?

winter quartz
#

So the trick you wanna do is distribute x on the LHS

#

Then see of you can get terms with y in them on their own side. That is:

$cy+ky=\dots$ where c and k are some random constants.

obsidian monolithBOT
#

dackid

winter quartz
#

But of course, they are very specific in this problem

woven ravine
#

So now that we got (cy-a)x=ay+b

#

We can inverse the x and y to get the value

#

This is how I interpreted it based on you fellas” hints

winter quartz
#

You got it!

#

Also keep in mind, this is the inverse, so $f^{-1}(x)=\frac{ax+b}{cx-a}$

obsidian monolithBOT
#

dackid

winter quartz
#

But since $f(x)=f^{-1}(x)$, f is symmetric across y=x

obsidian monolithBOT
#

dackid

woven ravine
#

aha,i see thanks bro!

sterile wedge
#

Can someone help me with 37 please

main cedar
#

build a triangle where one of the angles is 'y' and then find the sides of the triangle

#

do you need further explanation?

sterile wedge
main cedar
sterile wedge
main cedar
#

ayy correct

#

awesome

sterile wedge
#

and then from there I get all the sides and then get the tan of the triangle?

main cedar
#

yes

#

keep in mind that you have (1-x) here, not (x)

sterile wedge
sterile wedge
main cedar
#

go ahead

sterile wedge
#

from the picture I posted earlier for number 41 I messed up on the x+1/2 but I don't know how to correctly do it. I know that I need to combine them somehow so I can get my 2 sides but I got x+2 which is wrong

main cedar
#

type in your steps

#

so i can see where you made a mistake

sterile wedge
#

I did (x+1/2)/1 and then multiplied the 1/2 and denominator by 1/1 and got x+2

main cedar
#

wait what

#

so your opposite side is x + 1/2 and your hypotenuse is 1

#

(idk what your step did, but x+ 1/2 would simplify into (2x+1)/2)

sterile wedge
#

wait I can just leave it as (x+1/2)/1?

main cedar
#

yes

sterile wedge
#

and ohh I was way off with the simplifying

main cedar
#

its a ratio so it doesnt really matter

sterile wedge
#

for some reason I thought I had to combine them

#

sorry for the bad question thank you for helping!

main cedar
#

again, no problem lol

gilded oasis
#

Yo what topics are under precalculus?

main cedar
#

read the channel info

gilded oasis
#

you mean #info or am I missing something

#

oh nvm found it

#

mobile sucks 🗿

strange plinth
#

Prove that if a^2+bc≠ 0, then the graph of f(x) = ax+b/cx-a is symmetric about the line y=x. Can you help me with this problem please?

native creek
#

Please show me how ro do thia

#

This

swift mountain
#

assuming that's x+4 on the right hand side, collect the x terms

trim hemlock
#

is this a test?

main cedar
#

everybody hates i. try rationalizing the denominator

trim hemlock
#

and wrong category

arctic walrus
#

It's review for a test

trim hemlock
#

the paypal part makes this skeptical catthonk

arctic walrus
#

The teacher didn't upload his lectures for that week

#

I mean, I have the textbook. But my friend comes over in an hour or less. I'd much rather buy someone a coffee to get it done tonight and not worry about it. But I can just go through my textbook as well

trim hemlock
#

welp, just like el chupacabra suggested

#

divides them and get rid of the i in the denom

#

try to use conjugates in the process as well

arctic walrus
#

God, I have no idea what that even means. Guess it's textbook time

main cedar
#

@arctic walrus im assuming you know how to rationalize complex fractions

arctic walrus
#

no i dont XD

main cedar
#

do you know what i^2 is

arctic walrus
#

It's fine, i'll learn the old fashioned way

#

Nope

main cedar
#

bruh

#

do you know what i

#

is

arctic walrus
#

I don't want to waste anybody's time to teach me an hour for a cup of coffee

#

An imaginary number or a vector

main cedar
#

i dont need a cup of coffee. im just tryna help

#

what is the definition of i

arctic walrus
#

Im so sorry, hold on, I did not expect such a quick reply. I am reviewing a previous section

#

I do have a question though

#

How do i distribute the second part correctly?

#

is it -9i - 12j?

main cedar
#

yes it is

#

ayo

arctic walrus
#

WTF

#

There's a distributive error here, is there not?

#

The 2j was distributed with a negative, and re-distritubed again..

main cedar
#

nah i dont see anything wrong

#

the - was only distributed once

arctic walrus
#

OH WAIT. It makes sense.... They distributed it to the second part first, then the first part last

uncut mulch
#

just seems there's a stray )

main cedar
#

the () doesnt include the 4j anymore after the first distribution

arctic walrus
#

That's what was confusing.....

main cedar
#

theres an extra ) for no reason

arctic walrus
#

Thank you you guys are great lol

main cedar
#

complex time

arctic walrus
#

not yet

#

it's directional angle time D:

#

i got it tho. hold up 🙂

main cedar
#

post this shit in the right section bruh

#

this isnt precalc

arctic walrus
#

Oh, sorry. I'm in PRECALC 2 right now.

#

So confused

harsh cipher
#

Hi

#

can someone help me with a question

kind horizon
#

Hi guys! this week i started learning complex numbers, but it's a huge confusion for me. So i don't understand the part why negative roots exist since we learned that we don't have a solution for the quadratic equation when the answer is negative. Can someone pls explain me a bit? Thankyou!

sick steppe
#

and fundamental theorem of algebra says there are always 2 roots to a quadratic

#

Your teacher likely said no R roots exist if b^2-4ac<0

sick steppe
#

yeah, that's not "there are no roots period"

#

No roots vs no R roots are different

kind horizon
#

and how come i^2=-1

copper musk
#

by definition

kind horizon
copper musk
#

yes you can

winter quartz
#

It seems so simple, but complex numbers is like a whole new world in comparison to the reals.

wispy aurora
#

A WHOLE NEW WORLD

hallow thunder
#

they are unreal

winter quartz
timber ice
#

Hey guys, i have a calculus question about a integral rule and i wonder is it ok to ask here or should i wait for a question channel?

#

i just need the name of the rule :3

timber ice
#

what is this rule called?

proud raven
#

its unclear what the rule is but are you thinking of u sub

timber ice
#

basically you use it when you want to integral a rational function

proud raven
#

quotient rule?

timber ice
#

all i get is partiell integral

#

let me look it up one sec

#

yuuup

#

that its

#

thank you!

#

I knew how to use it before but i totally forget about it for some reason lol

proud raven
#

you should

#

its a bastardized version of chain rule

timber ice
#

i just can't seem to get it to work

#

i knew how to do it before but for some reason it does not make any sense to me

proud raven
#

rederive it

timber ice
#

and all i see on youtube is partiel integration and u-substitution which is something that i don't need for this course

proud raven
#

$\int \frac{ f(x) }{ g(x) } \dd x $ ?

timber ice
#

$\int \frac{ f(x) }{ g(x) } \dd x$

obsidian monolithBOT
#

steppaz

proud raven
#

fugc

timber ice
#

hehe

#

but like

#

look at this

proud raven
#

$\int f(x) \cdot g(x) ^{-1} \dd x $

#

this is what i meant

#

idk whats up w texit

timber ice
#

if you look at b)

#

where does 1/2 come from?

proud raven
#

u sub

timber ice
#

i remember something about moving out the denum outside of the integral but that doesn't seem to work and stuff would cancel out

proud raven
#

$2 \cdot \frac{1}{2} = 1$

obsidian monolithBOT
#

jan Niku

proud raven
#

youre only looking at the 1/2

#

consider the 2 as well

#

i guess really theyre also applying the constant multiple rule

#

$\int x = \int \frac{1}{2} \cdot 2 \cdot x = \frac{1}{2} \int 2 \cdot x$

obsidian monolithBOT
#

jan Niku

proud raven
#

which you want there because 2x is the derivative of x^2+1

#

alternatively, you could do u sub first and get to a similar answer

timber ice
#

yeah i'm with you with the 2x is integral of x^2+1

proud raven
#

which is probably better since the approach yo showed requires you to have some foresight

#

well

proud raven
#

x^2 + C is the integral of 2x

timber ice
#

the course contains derivatives and integrals but no u sub

#

or partiell integration

proud raven
#

u sub is necessary

#

well maybe not

timber ice
#

tell that to my teacher haha

proud raven
#

but its a good idea i think

#

,w partiell integration

obsidian monolithBOT
timber ice
#

there is literally 5 or 6 pages about the substitution method in my book

proud raven
#

oh

#

parts

#

i had no idea this had a better name

timber ice
#

😄

proud raven
#

parts is a really dumb name

#

eh just watch some videos

timber ice
#

i think it sounds cool

#

Partiell integration

proud raven
#

u sub is really just algebra disguised as calculus

timber ice
#

integration sounds cool in general

#

alrighty lets see if i can find some videos of it

proud raven
#

khan academy maybe or

#

theres no shortage of calculus tutorials

timber ice
#

Yes, thank you

proud raven
timber ice
#

AH

#

found it

#

it's called "Reciprocal rule" or just "Reciprocal"

#

there is a perfect 2 minute video that explains exactly how it works hype

winter quartz
#

This isn't quite a rule, it is just a lucky u-substition

sick steppe
#

yeah it's just u-sub

pliant locust
#

That is not the reciprocal rule. That is just a standard integral recall that in highschool we were taught that the derivative of ln(x) = 1/x. This integral is just a generalized version which you get through u-substitution.

Reciprocal rule is a rule for differentiation not integration.
Pic related is kvotregeln.

rustic glacier
#

could someone please help w the polar equation of a parabola with its focus at the pole and vertex at (1, -pi/2)?

#

I don't really understand why p is 10 instead of 5 and how the directrix is to the left of the pole

timber ice
pliant locust
# timber ice Then how would you take the derivative of a rational function without using the ...

I was just saying that
$\int{\frac{dx}{x}} = \log{\abs{x}} + C \
\int{\frac{f'(x)}{f(x)}} = \log{\abs{f(x)}} + C$
Isn't called the reciprocal rule, reciprocal rule is for differentiation. This integral is just a standard integral, an identity that pops up when solving some integrals which you can reuse. There are a list of standard primitives you have to your use when solving integrals. I assume your book has a proof of the integral somewhere.

obsidian monolithBOT
pliant locust
#

For example, this integral
$$\int{\frac{e^{x}dx}{1+e^{x} } }= \log{\abs{1+e^{x}} } + C$$
I identified that the numerator is the derivative of the denominator so i applied the standard integral $$\int{\frac{dx}{x}} = \log{\abs{x}} + C$$ to solve it

obsidian monolithBOT
timber ice
#

Oh

#

It says that any rational function has the integral of f'(x)/f(x)= ln I f(x) I + C

pliant locust
#

Yeah no biggies, you can say it is rule i just didnt want you to confuse it with the reciprocal rule in the youtube video you linked which was him just differentiating a rational function

dark sky
#

how would you graph overall shape of this by hand

viscid thistle
#

What's 9+10

odd rivet
dark sky
#

ok i did that

#

but what do i do after

odd rivet
#

So u can plot a rough graph using that info

#

And see as x tends to -inf and +inf

#

If f(x) tends to 0 or inf or whatever

pliant locust
#

You find the intercept points, find the stationary points by having the derivative, then solve the limit as x approaches infinity and negative infinity

#

lastly

#

check for vertical asymptotes by checking what happens to a function as it approache a singularity. (a singularity in this case is divison by zero). You have singularities at x = -8 and x=3, Solve the limit of the function when x approaches 3 and when x approaches -8 both from left and from right.

#

If it equals infinity you have a vertical asymptote.

#

If the limit exists from right but it equals infinity from left then the function approaches an open endpoint from right but it will be a vertical asymptote from left.

dark sky
#

Ok thanks

#

What’s the end behavior of this function?

#

Is it as x approaches -infinitely, y approaches positive infinity and as x approaches infinity, y approaches negative infinity?

uncut mulch
#

technically true, however it seems like an oblique asymptote would best represent what's happening

rancid crest
#

can uh

#

someone help me with this

#

i know you can factor it

#

cosx(sinx + 1)

#

set that to 0

#

cosx = 0

#

sinx = -1

hallow thunder
#

you can do inverse sin/cos here

#

then consult the graph to find the other values between 0 and 360 degrees

#

or unit circle

rancid crest
#

wdym

#

how would i do that

hallow thunder
#

here is how i would do it for cosx

pliant locust
rancid crest
#

3pi/2

#

and pi/2

#

90 or 270

pliant locust
#

So what is the problem? 😄

rancid crest
#

uh

#

um

#

is it just 270

tall cloud
#

Can I get help with this question please?

pliant locust
rancid crest
#

right

#

but only 270 meets both of requirements so thats where im sorta confused

pliant locust
#

I see

rancid crest
#

ye

pliant locust
#

Well if x=3pi/2 implies sin(x)=-1
Then i can say sin(x)=-1 for x=3pi/2 + 2*n*pi
where n is an integer since sin is periodic.

rancid crest
#

hm

pliant locust
#

If i rotate 360 degrees i end up in same place

#

2pi = 360 degrees

rancid crest
#

as you go through the unit circle

#

90 would technically still work

#

?

pliant locust
#

yeah you get zero whenever cos is zero aswell

rancid crest
#

alr so imma put 90 n' 270

pliant locust
#

remember to include all solutions since it is periodic

rancid crest
#

it says 0 < theta < 360

pliant locust
#

Well then should be those two then

rancid crest
#

oki

crimson cedar
#

Yo, if you have dy/dx of two graphs, how do you use that to find where the gradient is the same?

pliant locust
#

you mean slope?

#

if f and g are two function, just solve for x

#

where
f'(x) = g'(x)

rancid crest
#

what does simplest radical form with a rational denominator mean..

#

my answer is sqrt30/10

pliant locust
#

what is the question

rancid crest
crimson cedar
crimson cedar
pliant locust
#

ye

crimson cedar
#

does x = -1/2 seem right for that? idk if thats right at all lol

pliant locust
#

Well the derivative of a function at point x=c will give you the slope of the line that tangent the graph at x=c

#

The function x is its own tangent, recall the equation of a linear function being kx+m where k represent the slope

#

and k = delta y / delta x

crimson cedar
#

-1/2 is the slope for the tangent cause x is the slope of that norm right?

pliant locust
#

yeah

rancid crest
#

sooo

#

wa

pliant locust
#

sorry man, i am not sure what they mean by rational denominator

#

I agree with your answer but then again im not sure

main cedar
rancid crest
#

yea

#

i did it

#

so

#

we good

main cedar
#

oh ok then

lilac storm
#

ln(1/2)/-27 can anyone simply just help me on how do you simplify this?

#

i know that the answer is ln(2)/27 but i just need a little help on how do you get from ln(1/2)/-27 to ln(2)/27

uncut mulch
#

apply power rule to ln(1/2)

lilac storm
#

so how do i do that?

#

so what i have been trying to do is taking the reciprocal of the denominator meaning i did ln(1/2) times -1/27 which gives me ln(-1)/54, but this isn't the correct answer

uncut mulch
#

1/2 = 2^(-1)

lilac storm
#

sorry i don't get what does that mean?

uncut mulch
#

$\ln(\frac12) = \ln(2^{-1})$

obsidian monolithBOT
#

ℝamonov

lilac storm
#

yes i got it

#

so after getting ln(2^-1), what do i do next?

#

so i have ln(2^-1)/-27

uncut mulch
#

power rule (for logs)

lilac storm
#

so how would i start, if you could help me?

uncut mulch
#

do you know your log laws?

lilac storm
#

yes

uncut mulch
#

specifically the

power rule (for logs)

#

and can you apply that to:
ln(2^(-1))

lilac storm
#

i know them but i just can't remember them at the moment

uncut mulch
#

if you know them, you should be remember them

#

if not you should look them up

lilac storm
#

do i do like ln(2^-1/27)

uncut mulch
#

as i've mentioned power rule/law (for logs) 5? times already

#

no

#

now you also need to review your order of operations

unborn blade
#

Can someone walk me through how to do something like this?

uncut mulch
#

you could start with
2x + b = x^2 -4
and then consider the value of the discriminant

median ivy
#

cos2A = 3/5 right?

sick steppe
timber ice
#

Hi, i just have a question about limits as they approach +/- infinity. I was wondering when you want to examine how a function behaves when it goes towards +/- infinity is there some condition that the function has to fulfill for *you * to examine how it behaves when it goes towards +/- infinity?

#

If this question should go under question channel lmk :p

#

Like, as i understood it, the values will still be the same whether it goes towards +/-

#

For example if we look at this function, i believe they have done some polynomial division to figure out the asymptote. Is this just some type of preference to write it as +/-?

#

if you'd answer please tag me catthumbsup

lilac storm
#

so for this question this is what i have done so far, so i think i have solved half of the question

#

so i have solved for k but now i don't know what to do next, like what is my next step going to be.

#

if anyone is there that can please help me?

#

i also have the answer key for this so the answer key says the answer k=ln(2)/27, which i have gotten already and then the actual question finding the time which is 54 years which i don't know how to find, like i don't know the next step to find it?

#

anyone there to help please?

#

anyone there...?

viscid thistle
#

Does anyone know how to do this? I'm so confused

hollow zenith
#

U could start by modelling the question into an equation first!

pliant locust
# timber ice Hi, i just have a question about limits as they approach +/- infinity. I was won...

You have three cases:

One where if x approaches a value c implies f(x) approaches value C then the limit is C however if the function approaches infinity when x approaches c then you have a vertical asymptote (lodrät asymptot). You also have to consider two-sided and one-sided limit when studying the limit as x approaches a singularity. (Singularities in calc 1 are for those x where the function isnt defined, for example, division by zero, negative argument to squareroot or logarithm , or x-values that are outside the domain of certain trig functions for example x<-1 is undefined for the explicit function arcsin(x).

The third case is when x approaches infinity, this is when you study if the function has a horizontal asymptote(vågräta asymptoter). If x -> infinity implies f(x) -> C then C is a horizontal asymptote of f(x). However if x->infinity implies f(x)->infinity then you dont have a horizontal asymptote.

To sum up:

  1. When x->c you are checking for vertical asymptotes at x=c (You always check left and rightside limit.)

  2. When x->infinity (from left and from right) you are checking for horizontal asymptotes.

As to how you compute certain left-side and right-side limit i will link a post where i explained an informal way of doing it. The right way is using epsilon-delta proofs.

timber ice
#

shit

pliant locust
#

We can begin by just doing one of the limits

timber ice
#

so when i check for vertical asymptotes i check for x as it approaches infinity from left and right

pliant locust
#

No

#

That is horizontal

timber ice
#

oh

#

when x approaches c

pliant locust
#

Yeah

timber ice
#

and for horizontal it's when it approaches infinity from left and right

pliant locust
#

And c in this case is the x that makes the function undefined

timber ice
#

sorry i am a bit snurrig rn sadcat

#

lol

pliant locust
#

Ye np,

timber ice
#

That's very well written, i always just check for infinity

timber ice
#

does it mean it goes towards -3 from the left side?

pliant locust
#

Yes

#

3^- can be interpreted as
3 - d where d is a very small number

#

And 3^+ is 3 +d where d is a very small number

timber ice
#

and the values don't really change tho right? when you check for infinity from left and right, you could just add ^- and ^+ as soon as you have figured out what value it goes towards

timber ice
pliant locust
#

Solve limit as x approaches positive infinity

And now solve the limit as x approaches negative infinity

#

The limit is infinity when x approaches infinity right

#

But when you are going towars negative infinity you will have the limit equal 0

#

Therefore y=0 is a horizontal asymptote to e^x

#

Which is just the x-axis

timber ice
#

försöker bara förstå vad som står :p en sekund xd

#

oh

#

juste

#

because e is defined for e>0

#

so right side is infinity whiles as minus infinity is 0

#

so it can differ

pliant locust
#

e is defined for all x

#

Hold on i will draw

#

Ok let me ask, how do you evaluate the limit 1/x as x approaches 0 from left?

timber ice
#

let me get paper

#

it goes towards +/- infinity if x=/0 or x=/1

#

it goes towards 1

#

because like

pliant locust
#

solve specifically for x -> 0^-

#

What is 1/ (0 -0,01) equal to?

timber ice
#

it becomes -1000

#

it goes towards -infinity, i'm not sure how to explain it but it get's bigger and bigger

pliant locust
#

Exactly

timber ice
#

but negative

pliant locust
#

Or well 0-0,01 is -0,99 right

#

And the smaller i make d the larger a negative

#

And if i go from right
x->0^+

#

It is 1/(0+0,01) which is 1 divided by a positive very small number

#

Which gives you a positive infinity

#

Now

timber ice
#

yeah

pliant locust
#

To go back to e^x

#

How do you solve e^x when x approaches negative infinity

timber ice
#

well it goes towards +infinity right?

#

the numbers decrease but never reaches negative

#

no

#

it goes towards 0

pliant locust
#

e^-x = 1/e^x right

#

So it goes towards 0

#

Since x is approaching infinity we know that 0 is a horizontal asymptote

timber ice
#

yeah

#

damn

pliant locust
#

Lets skip horizontals for now

#

Lets just do verticals

timber ice
#

yeah please

pliant locust
#

Consider the function: 1/(x-5)

timber ice
#

let me actually check which is which one sec

pliant locust
#

What is it domain? Is it defined for all x?

timber ice
#

it's not defined for when x=5

#

At 5 we have a vertical asymptote

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oh yeah i remember now, vertical asymptote is when the nämnare is 0 and horizontal is as it approaches infinity.

pliant locust
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Yeah, so for x=5 the function isnt defined, x=5 is a singularity we want to study

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usually it implies there is a vertical asymptote but that is not always true

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You have to confirm it by solvind the limit

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So lets solve what is the limit when we approach 5 from left respectivelt from right?

timber ice
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it's 5^- and 5^+, no?

pliant locust
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Ye

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So what does the function approach when approaching 5 from left?

timber ice
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it approaches minus infinity right?

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if we plug in 1/(4.99-5) we get -100 and it continues to decrease

pliant locust
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Exactly

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Good

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Looks like we are getting somewhere!

timber ice
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yeah xD

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i am starting to get the hang of it

pliant locust
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Since we have infinity from left and right

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We have confirmed that there is a vertical asymptote at x=5

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Now lets see of our function has a horizontal asymptote

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Lets start with positive infinity

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Solve 1/(x+5) when x approaches positive infinity

timber ice
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it's 0

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vågrät asymptote at 0

pliant locust
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Both from left and right ye

timber ice
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since we can't breake out any 0's

pliant locust
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One divided by a very big number gets us zero

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And one divided by a very big negative number gives us 0 aswell

timber ice
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and these asymptotes are basically these values that the function never touches

pliant locust
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Yeah

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So vertical asymptotes are at valdes where x approaches a value that is in the domain

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While x when approaching infinity we are checking for horizontal asymptotes

timber ice
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ah i see now

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So that's basically what my teacher was doing in that question

timber ice
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she is looking for when x=c which was our scenario one

pliant locust
timber ice
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Du är fan tvär bra 😳

pliant locust
floral remnant
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hmm

lilac storm
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so for this question this is what i have done so far, i think i have solved half of the question

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so i have solved for k but now i don't know what to do next, like what is my next step going to be

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if anyone is there that can please help me?

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i also have the answer key for this so the answer key says the answer k=ln(2)/27, which i have gotten already and then the actual question finding the time which is 54 years which i don't know how to find, like i don't know the next step to find it?

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if anyone is there that can please help me out?

pliant locust
lilac storm
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so i don't get how would i do it?

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like have i done everything correctly so far because i have only solved for k so far?

pliant locust
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Let $N_{0}$ be the safe level of the substance. We know it is four times the safe level, so $Q_{0} = 4N_{0}$ We know that $Q(t)= Q_{0} \cdot\left(\frac{1}{2}\right)^\frac{t}{27}$
then solve the follwing equation.
$$Q(t) = N_{0}$$
$$ N_{0}= 4N_{0}\cdot\left(\frac{1}{2}\right)^\frac{t}{27}$$

obsidian monolithBOT
lilac storm
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so i don't have the initial value which is No so how will i solve for t(time)?

pliant locust
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$$ N_{0}= 4N_{0}\cdot\left(\frac{1}{2}\right)^\frac{t}{27}$$
$$ \frac{1}{4}=\left(\frac{1}{2}\right)^\frac{t}{27}$$
$$ \log{(\frac{1}{4})}=\log{\left(\left(\frac{1}{2}\right)^\frac{t}{27}\right)}$$

obsidian monolithBOT
lilac storm
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sorry, where did No go?

pliant locust
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I divided both sides with 4N

lilac storm
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oh i got it

pliant locust
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then i log both sides

lilac storm
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yes your right

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so after taking the log of both sides, are you left with log(1/4)=(1/2)^t/27?

pliant locust
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Im left with the latest row in above pic

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Should be straightforward now on how to isolate t

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the t is your unknown

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Recall that:
$$\log{x^a}= a\cdot \log{x}$$

obsidian monolithBOT
lilac storm
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so is it log(1/4)=(t/27) x (1/2)?

pliant locust
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what happened to the log on RHS?

lilac storm
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doesn't it go away when i bring down the exponent?

pliant locust
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nope

lilac storm
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oh no, my bad