#help-10

1 messages · Page 133 of 1

woven creek
proven oar
#

you will get A = area of square + area of rectangle

sinful saffron
#

that would leave the first sqare with w: x, l: x, then the second rectangle: w: 2x, l: 2x + 1

proven oar
#

yes

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so then for the area you would get

sinful saffron
#

so w: 3x, l: 3x + 1

proven oar
#

is this

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for the whole shape?

sinful saffron
#

yes

proven oar
#

how did you get this

sinful saffron
#

i added w and l together

proven oar
#

if you are trying to find the area

#

then you need to find the area of the individual shapes

sinful saffron
#

so the rectangle would be 4x + 1

proven oar
#

no

sinful saffron
#

or squared

proven oar
#

can you tell me what the formula for area of a rectangle is

#

and formula for area of a square

sinful saffron
#

a = l * w

proven oar
#

correct

#

so going back to what you said before

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width of the rectangle is 2x+1

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and length of the rectangle is 2x

sinful saffron
#

2x + 1 * 2x

proven oar
#

yes

sinful saffron
#

like terms: 2x * 2x

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4x^2 + 1

proven oar
#

That isnt correct

#

when you sub the values into the formula you get

#

A = (2x+1)*(2x)

#

can you tell me what the expanded form of this would be

sinful saffron
#

uh 1 sec

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2x(2x+1)

#

i entered it in my calculator thats what i got

proven oar
#

That is correct

#

however that is not entirely expanded

#

do you know how to expand brackets

sinful saffron
#

yeah

proven oar
#

ok

#

so how would you expand

proven oar
sinful saffron
#

2x^2+2x

proven oar
#

correct

#

so thats the area of the rectangle

#

how would you find the area of the square

sinful saffron
#

same formula

proven oar
#

oh wait

#

sorry

#

there is a mistake

sinful saffron
#

oh

proven oar
#

2x^2

#

this should be something else

sinful saffron
#

4x^2

proven oar
#

nice

sinful saffron
#

mb

proven oar
#

so now you have area of rectangle (4x^2+2x)

#

how would you get the area of the square

sinful saffron
#

x^2

proven oar
#

nice

#

so the total area of the shape would be?

rain forge
#

?

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Hum not sure

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This is not a square or am i wrong?

sinful saffron
#

6x^2+2x

rain forge
#

Like it's more x and x+1

proven oar
#

The total area would be

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(x^2) + (4x^2+2x)

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so collecting like terms

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you would get

rain forge
#

Bro i don't think

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Or am I wrong

sinful saffron
#

5x^2+2x

proven oar
#

Yes

#

nice

#

that should be the final answer

sinful saffron
#

idk why but i read it as 2x^2 mb

#

the answer sheet says 5x2+3x hmmmm

rain forge
#

I would say 5x² + 3x

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Bro you get wrong@proven oar

sinful saffron
#

how did u get the 3x?

rain forge
#

It's not a square

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It's 2x+1-x

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So the length are x and x+1

proven oar
#

oh tru

#

mb

sinful saffron
#

oh yeah forgot about that 1

rain forge
#

Or you can do $3x*(2x+1)-x²$

proven oar
#

its a rectangle not a squarte

warm shaleBOT
#

phoestaclies

proven oar
#

So area instead would be x(x+1) + 2x(2x+1)

rain forge
#

Yes

sinful saffron
#

ah that makes sense now

proven oar
#

Anything else I can help with

sinful saffron
#

all good thanks tsym

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phoestaclies ty for assisting

rain forge
#

Np good luck 👌

sinful saffron
#

ty

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well i shall close this now

#

.close

obtuse pebbleBOT
#
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open mango
#

Hello everyone if someone know how to solve this question?

obtuse pebbleBOT
#

@open mango Has your question been resolved?

open mango
#

NO

#

@obtuse pebble nope

timid silo
#

Lable the diagram first

#

Would be easy to communicate if someone helps you out

open mango
#

Ok

obtuse pebbleBOT
#

@open mango Has your question been resolved?

obtuse pebbleBOT
#

@open mango Has your question been resolved?

obtuse pebbleBOT
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@open mango Has your question been resolved?

obtuse pebbleBOT
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brisk kayak
obtuse pebbleBOT
brisk kayak
#

How do I do question 6

gleaming ridge
brisk kayak
#

calculate for y prime

thick gyro
#

so differentiating it

brisk kayak
#

yeah

thick gyro
#

for question 6

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do you know

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what the diffferential of

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inverse cos is

brisk kayak
#

1/cosx

thick gyro
#

no

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that is arccos

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as in, the actual inverse cos

brisk kayak
#

sin?

thick gyro
#

no

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as in

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if cos(pi/2) = 0

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then cos^-1(0) = pi/2

gleaming ridge
#

Clearly she doesn't know

thick gyro
#

that was learnt in standard trig years before differentiation was taught

gleaming ridge
#

well, you can divide both sides by x and then take cos of both sides

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cos will cancel with cos inverse

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then differentiate using product rule and rearrange

thick gyro
#

i dont think the person knows how to do implicit differentiation

gleaming ridge
#

She won't be able to do question 8 without that

thick gyro
#

guess youre right

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but honestly, she just needs to know what the differentiation of arccos is, and then can just use product rule normally

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instead of

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trying to derive it for xarccosx

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would be less work

gleaming ridge
#

another option is to derive the derivative of arccos separately and then use it freely

brisk kayak
#

So how do I solve it?

#

.close

obtuse pebbleBOT
#
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solid topaz
#

how do I factor x^4 + 2x^3 - 16x^2 - 32x?

obtuse pebbleBOT
heavy depot
#

$x^4+2x^3-16x^2-32x$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

this?

fickle turret
#

Factor out an x and guess a root

heavy depot
#

first take the x out

thick gyro
#

to see which roots to guess

heavy depot
#

$x(x^3 + 2x^2 - 16x -32)$

warm shaleBOT
#

CrEpasPmkinPie

solid topaz
thick gyro
heavy depot
#

now you can split that cubic equation

#

$x((x^3+2x^2)+(-16x-32))$

warm shaleBOT
#

CrEpasPmkinPie

thick gyro
#

thats acc genius, but not much equations are that obviouss

heavy depot
#

and now take common factors from both parenthesis

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and do some algebra to it

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$x( x^2(x+2) + -16(x+2))$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

some rearranging shows the factors

#

$x(x^2-16)(x+2)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

and even that x² factor could be split up

solid topaz
#

To be factored in a way that I could use for the graphing for the polynomialss

heavy depot
#

$x(x-4)(x+4)(x+2)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

and those are your zeroes aswell

thick gyro
#

honestly, rational root theorem gives me all the roots in this case

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-2, -4, 4

heavy depot
#

and 0

thick gyro
#

so i just know to split it up into (x+2)(x+4)(x-4)

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although if it only gave me 1

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id have to do polynomial long division

heavy depot
#

do synthetic instead

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its a linear divisor

thick gyro
#

never heard of it

heavy depot
#

it's a lot easier than long division

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take the polynomial

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then take a linear factor

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must be linear

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and the polynomial has to have every degree

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so put zeroes in as coefficients

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then take the opposite of the constant in the factor

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its funky

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take this polynomial

solid topaz
#

Wait can u do the factoring step by step

heavy depot
#

sure

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$x^4+2x^3-16x^2-32x$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

each of those terms has an x

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so you can factor the x out

solid topaz
#

ohh ok

heavy depot
#

$x(x^3+2x^2-16x-32)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

now that's a cubic polynomial

#

so split the two halves

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$x((x^3+2x^2)+(-16x-32))$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

and now you can take common factors out of both of those

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$x(x^2(x+2)+-16(x+2))$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

and the do some algebra (I don't remember what it is exactly)

solid topaz
heavy depot
#

ah

#

$(-16x-32)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

that has a common factor of -16

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so divide both terms by -16

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$-16(x+2)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

$\frac{-32}{-16}=2$

warm shaleBOT
#

CrEpasPmkinPie

solid topaz
#

or can u help me do it from the point where I need to graph it

#

like the behavior of the graph

heavy depot
#

$x(x-4)(x+4)(x+2)$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

those are the zeroes

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${-4,-2,0,4}$

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

The leading coefficient is also positive

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so it will open upwards

solid topaz
#

upwards since its greater than 0?

thick gyro
#

donr use someonee elses chat

solid topaz
#

Since idk where to start, to be able to graph it

solid topaz
heavy depot
#

there is no imaginary root

solid topaz
#

there's another thing that Idk how to solve

#

The volume of a rectangular packaging box is 73dm^3 more than the volume of a cube
packaging box. The length of the rectangular box is 1dm longer than twice the edge of the cube.
Its height is 2dm shorter than the length of the edge of the cube. Its width is 1dm longer than the
cube’s edge. What are the dimensions of the two packaging boxes?

obtuse pebbleBOT
#

@solid topaz Has your question been resolved?

obtuse pebbleBOT
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timid silo
#

Find all real solutions and justify your steps $1 < \ceil{3x+5} \leq 3$

warm shaleBOT
#

hibyehibye

timid silo
#

So I did this by just letting f(x) = 3x+5 and finding the preimage of (1,3]

#

but im not sure how I’m meant to actually solve it and justify all my steps

rigid lintel
#

thats partially correct

#

its correct for the <= 3 part

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but not for the 1 < part

timid silo
#

hmm

rigid lintel
#

because of the ceiling function

timid silo
#

oh i meant f(x) = ceil(3x+5)

rigid lintel
#

oh alright then youre good

timid silo
rigid lintel
#

definition

timid silo
#

definition of what?

rigid lintel
#

$1 < \ceil{3x+5} \leq 3$ is equivalent to $x \in \mathbb{R}$ such that $f(x) \in (1, 3]$

warm shaleBOT
rigid lintel
#

with $f(x) = \ceil{3x+5}$

warm shaleBOT
timid silo
#

Tysm!!!

#

.close

obtuse pebbleBOT
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dark surge
#

how would i go about disctreticizing a partial derivative like this (from the euler equation) $\frac{{\partial u}{\partial x}}, where x is the grid spacing in the x direction and u is the velocity vector$

warm shaleBOT
dark surge
#

wait

timid silo
#

stop the $ before u get into the text

dark surge
#

$\frac{\partial u}{\partial x}$

kind hawk
#

essentially just do it in both directions separately and then add together

warm shaleBOT
kind hawk
#

do you know the multidimensional taylors theorem?

#

oh wait you don't have a mixed derivative

knotty crow
#

you can also use

kind hawk
#

I read too much

warm shaleBOT
#

Modus

$$\pdv{u}{x}$$
karmic bison
#

Can any one help me with a short assignment

dark surge
kind hawk
#

then why are you doing it

dark surge
#

because i want to understand it

#

where do i even start with such stuff

kind hawk
#

well you are probably missing like 3-4 years of basics

timid silo
dark surge
#

but how is this supposed to be done

kind hawk
#

by knowing the basics

#

what exactly do you want to hear here

dark surge
#

the ones with the polynomial equations i understand

#

its just that this is a vector and a grid spavincing

kind hawk
#

"the ones with the polynomial equations" ?

dark surge
#

where you have f(x,y) and you have to do $\pdv{f}{x}$

warm shaleBOT
dark surge
#

and the normal ones too dx/dy

#

but i dont understand how we go from a function to having a vector

kind hawk
#

a vector is just a couple of functions stacked on top of each other

#

$u(x) = (u_1(x), u_2(x), \ldots, u_n(x))$ where all the $u_i(x)$ are "normal" functions

warm shaleBOT
#

Denascite

dark surge
#

oh

kind hawk
#

and you can treat each coordinate separately

dark surge
#

ah ok thanks, thats exactly the thing i need to know

#

.close

obtuse pebbleBOT
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fringe dew
#

x

obtuse pebbleBOT
fringe dew
#

Hello, i'm Mallow. I'm currently programming an isometric Chess Game for my school. And i'm a bit stuck with maths.
Has you see. I've got the "chess_board.png" scaled by 4 so it's 616x364. Using some rudes archaic paint skill. I've found the 4 coordinate of the corner :
A = [0, 132];
B = [386, 0];
C = [616, 232];
D = [232, 364];
And i got an x and y for the mousePointer on the image. So basically mouseX can be [0, 616] and mouseY [0;364].
I can't figure how to determine the x and y of one of the squares based on the mouse coordinate.
Can someone help me please ?

royal basin
#

is this image going to be hardcoded into the game, as well as the screen resolution?

#

one would think that you'd want to grab the coordinates of the mouse within the window rather than on the image.

#

maybe i am mistaken about this.

fringe dew
#

Yes, the image will always have the same resolution, but the screen size can change. Don't worry about that. The mouse value that will be forwarded to the calc fonction will be based on the image location. At image 0,0, cursor will be at 0,0

#

The problem is i'm trying to figure which square as been pressed. And for that i've figured to get the deplacement between this 2:

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left corner, and the right corner of the first square

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+50.875x -16.5y

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(the 0;0 point is the top left corner of the rectangle image)

obtuse pebbleBOT
#

@fringe dew Has your question been resolved?

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mild badger
obtuse pebbleBOT
mild badger
#

I need help on question 22

naive fossil
#

Have you tried using the Law of Sines?

mild badger
#

idk how to use it that way

#

i can only use it a certain way when i have 2 angles

high lily
#

consider law of cosines

#

which relates three sides of a triangle with an angle

mild badger
#

i havnt learned law of cosines

obtuse pebbleBOT
#

@mild badger Has your question been resolved?

obtuse pebbleBOT
#

@mild badger Has your question been resolved?

obtuse pebbleBOT
#

@mild badger Has your question been resolved?

obtuse pebbleBOT
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dark tundra
#

I got tripped up ont his problem. I dont understand why the largest integer is x+127

dark tundra
#

if its the sum of the first 127 integers

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x+0 is an integer

#

and then (x+1)….(x+126) are the other 126 integers

#

so wouldnt the largest term be x+126

timid silo
#

I dont really get their working out but you’ll get the same answer.

127x + sum 0 to 126 = 27178
x = 151
151+124=275

obtuse pebbleBOT
#

@dark tundra Has your question been resolved?

dark tundra
#

thanks alot

#

.close

obtuse pebbleBOT
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compact prawn
obtuse pebbleBOT
compact prawn
#

Can anyone help me with this? I just basically need to know what case it is and then I can do it after that

#

Well I know it’s non homogenous case

#

Wait I’m dumb I can do this

timid silo
obtuse pebbleBOT
#

@compact prawn Has your question been resolved?

compact prawn
#

I got this but I’m not entirely convinced it’s correct lol

#

I was not in class when this was taught and haven’t had the time to catch up so I’m not 100% sure what I’m doing 😅

timid silo
#

This is correct.

compact prawn
#

!close

#

!thanks

timid silo
#

.close

obtuse pebbleBOT
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storm wing
#

I have a question about one of the steps here. I think it's simple arithmatic

storm wing
#

Is there some basic math here that is making me miss how we are able to do this?

#

So I understand how sqrt(x+3) -sqrt(x) can be divisible by one

#

but i dont understand the rule that allows us to multiply it by sqrt(x+3) + sqrt(x) .sqrt(x+3) + sqrt(x)

#

Hopefully, that makes sense.

supple granite
#

Multiplied the conjugate of the numerator to rationalize the numerator

storm wing
#

Thank you for definining it for me. I can see how to do this online now. Thank you.

#

.close

obtuse pebbleBOT
#
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worldly trench
#

when I'm writing a math paper, how do I make it clear that the (1) I'm referring to is not part of the equation?

worldly trench
#

Like this, I want to reference it throughout my paper

frosty spoke
#

do people actually believe that it's in there?

worldly trench
#

Yes

frosty spoke
#

lord help us

worldly trench
#

😭 I thought it was clear enough

frosty spoke
#

you could maybe write (Equation 1) or some abbreviation

worldly trench
#

Do you have any suggestions for making it cleaer?

worldly trench
frosty spoke
#

like (E1) or (Eq 1)

worldly trench
#

Ah gotcha

frosty spoke
#

I honestly prefer the (1) though

#

didn't know people fell for that

worldly trench
#

What if it's not necessary an equation per se?

timid silo
#

if you're using LaTeX

worldly trench
#

I wrote that in google docs

timid silo
#

ah

obtuse pebbleBOT
#

@worldly trench Has your question been resolved?

obtuse pebbleBOT
#

@worldly trench Has your question been resolved?

#
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obtuse pebbleBOT
#
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open nimbus
obtuse pebbleBOT
open nimbus
#

how do i do (b) ?

supple granite
#

Well you have the center and the radius

open nimbus
#

yeah im just fucking stupid and forgot everything in algebra 2 apparently i just figured it out im sorry

#

thank you tho! ❤️

supple granite
open nimbus
#

.close

obtuse pebbleBOT
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livid agate
obtuse pebbleBOT
livid agate
#

How is that a?

shy cairn
livid agate
#

Oh crap

#

Yeah, just realize

#

Thank you

#

.close

obtuse pebbleBOT
#
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zinc zodiac
#

.reopen

#

hi?

obtuse pebbleBOT
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zinc zodiac
#

Does this make sense?

obtuse pebbleBOT
zinc zodiac
#

The x and y are for referencial use, that's why the subscripts

obtuse pebbleBOT
#

@zinc zodiac Has your question been resolved?

tardy epoch
#

yes it does

zinc zodiac
#

Could you please explain it to me? Like, i stays the same until j completes 4, and then i is 2 and the same happens, etc?

tardy epoch
zinc zodiac
#

Alright, thanks

#

.close

obtuse pebbleBOT
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wispy cave
#

In a circle of radius 2 miles, the length of the arc that subtends a central angle of 5 radians is

wispy cave
#

I know how to do the problem, but I'm not sure what 5 radians exactly is

#

I know how to convert degrees to radians and radians to degrees. but is 5 radians 5pi?

#

or

timid silo
warm shaleBOT
wispy cave
#

Ahh I see

#

So since I'm using s=r0 (theta) am I using 900/pi for theta?

timid silo
wispy cave
#

Ohhh I see

#

It did want it in radians but I just converted my answer back to radians

#

appreciate it

#

.close

obtuse pebbleBOT
#
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obtuse thunder
#

anyone...

obtuse pebbleBOT
#

Please don't occupy multiple help channels.

#

@obtuse thunder Has your question been resolved?

sullen raptor
#

Reciprocal

obtuse pebbleBOT
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clever temple
obtuse pebbleBOT
clever temple
#

I have a simple question

#

So

#

In that image

#

Sin(u) is set equal to x/sqrt of (1+x^2)

#

But why isn’t it just x?

#

Why do we have to divide by the hypotenuse?

gleaming ridge
#

cause the definition of sine in that it is ratio of perpendicular and hypotenuse

#

(sin is just short for sine) @clever temple

clever temple
#

Oh wait

#

Yeah i couldn’t think for a sec thanks so much

#

@gleaming ridge

#

Helped me solve the problem

#

.close

obtuse pebbleBOT
#
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gleaming ridge
#

sure

obtuse pebbleBOT
#
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red thistle
#

Don't mind that answer in there

obtuse pebbleBOT
red thistle
#

How do I go about getting the coefficients that should go in front of the 'y=e^rt"

#

I have the derivatives and the system of equations

fathom flicker
#

have you tried

#

y=Ae^(rt)

#

and then differentiating

#

and plugging in

#

and then solving for A

floral canopy
#

in the eq. above

red thistle
#

hold on lemme take a pic of what i did

#

i was thinking linear algebra but the uh

#

extra kinda stumped me

#

gimme a sec

fathom flicker
#

you can try aswell

#

y=xe^(rt)

#

is this just undetermined coefficients?

red thistle
floral canopy
#

how did you get to that

#

like the first line

floral canopy
red thistle
#

just strictly e^(rt) without the added t in front of the e?

#

ill try that

floral canopy
#

yea

red thistle
#

the way i was taught like two days ago

#

was when you have the original differential equation

#

which will turn out to r^2(r-4)^2

#

when its squared you'll have the

#

repeated roots

#

and just throw in an added t at the front

#

actually heres an example of what he did

#

anyway i digress, gimme a sec

fathom flicker
#

uhh

#

is the y^4 meaning the fourth derivative

red thistle
#

mhm

fathom flicker
#

oh

#

well

#

that changes a lot

red thistle
#

ah

fathom flicker
#

yeah, so then you do what your professor did

#

find the characteristic polynomial

#

which would be

#

r^4 -8r^3+16y^2 =0

red thistle
#

well that turns out to the 2nd pic that i did

fathom flicker
#

,, r^4 -8r^3+16r^2 =0

#

and you solved for the roots of ^ that

warm shaleBOT
#

AustinU

red thistle
#

mhm

fathom flicker
#

what'd you get

red thistle
#

r^2(r-4)^2

floral canopy
fathom flicker
#

so

#

it has two repeated roots

#

one at 0 , and one at 4

red thistle
#

i still dont know like the base answer to that, but because of the repeated roots

fathom flicker
#

so then the solution is..

red thistle
#

just throw in a t

#

Austin, as for what i got for trying, (albeit poor quality) was in the pic with the blue handwritten

#

maybe im getting lost

#

just

#

trying to figure out how to account for the uh

#

constants

#

given like

#

the third derivative that i found with the base form

#

y=e^rt

#

i dont know if i can solve for the constants

#

with linear algebra because of something like on the third derivative

#

48c4e^(4t)+64c4te^(4t)

#

he didn't show how to do it by hand either

#

just

#

"use technology"

#

trying to see if there is one by hand

fathom flicker
#

,, y=c_1+c_2t+c_3e^{-4t}+c_4te^{-4t}

#

this is what you got yes?

red thistle
#

no

#

idk why the third constant has c3e^-4t

#

is it simply because its a repeated root?

fathom flicker
#

so

red thistle
#
  • or - 4
fathom flicker
#

here's the deal

warm shaleBOT
#

AustinU

fathom flicker
#

when you have repeated roots

#

it tells you there is a solution

#

e^(-rt)

#

at that root

#

so from that we get the C_1 and the c_3 e^(-4t)

#

which I assume you follow

#

but

#

because this is a fourth order ODE

#

we know that

#

when we know one solution y_1 , to the ODE , there is another solution y=y_1u

#

where u is a function of t

#

the way you can solve for u

#

is writing

#

,, y=e^{-rt} u(t)

warm shaleBOT
#

AustinU

fathom flicker
#

we will take the case of our first repeated root at 0

#

,, y=u(t)

warm shaleBOT
#

AustinU

fathom flicker
#

now differentiate

#

,, y'=u'(t)

warm shaleBOT
#

AustinU

fathom flicker
#

etc.... etc...

#

plug in once you have them all

#

solve for the fact that 1*u(t) must equal 0

#

and you will end up getting (most likely) u(t)=t

#

and repeat the same process for your other repeated root

#

starting with

#

,, y=e^{-4t}u(t)

warm shaleBOT
#

AustinU

fathom flicker
#

differentiating 4 times

#

plugging in

#

solving for u(t)

#

and then you get your new solution

red thistle
#

trying to process all this
will the same initial setup for each derivative be the same, just with

red thistle
#

or

#

above

fathom flicker
#

I'm sending you an example image

#

although it is only for a second order ODE

#

this is for the case where we find a solution y=e^(-at)

#

so you would do this process twice

#

for the two repeated roots you had

#

y=1 and y=e^(-4t)

#

the method for solving in the simplest way I am assuming would be to follow the same pattern outlined with the blue pen

#

multiply the first line of the equation by a^4

#

then the second line by 4a^3

#

then the third by 12a^2

red thistle
#

ah ok i see how that pic is set up now then

#

uhm

#

well let me try my hand at this

fathom flicker
#

I actually think

#

it may be unnecessary to even solve the system

#

and that the case always becomes

#

u ^ whatever prime = 0

#

so then u(t) will become

#

the polynomial that arises from integrating it

#

,w y''''-8y'''+16y''=0

fathom flicker
#

so we get our ^ e^(4x) and e^(4x) * x type solutions along with our constant and constant * x solutions

red thistle
#

are the equations multiplied after we have found the derivatives then adding them together?

fathom flicker
#

that was the method there yes

#

^ although I think it is unnecessary

#

that was probably just the first proof in my notes of how it ended up giving the result

red thistle
#

hhmm

fathom flicker
#

See how there, the end result was u'' = 0 , and then integrating would give u=c1 t + c2

#

I think that you will always reach an end result of

#

something like

#

u'''=0

#

and for us it will be the fourth derivative

#

which will give

#

u=c1t^3+ c2t^2 +c3t+c4

red thistle
#

sorry i-

#

so with that u(t)

#

do we use that in tandem with something else to find the constants?

#

cuz if

#

well if t=0

fathom flicker
#

In order to solve for the initial values we first need to get the entire solution of our ODE, which we can do once we find the other two solutionst that aren't y=c1 and y=c2e^(-4t)

red thistle
#

agh
im feeling really dumb right now
Im not sure where to continue off with that right now

#

so to find the other two solutions

#

uhm

fathom flicker
#

Don't feel dumb , this is a struggle for me aswell

red thistle
#

hhm im still a bit lost with this new method

fathom flicker
#

lol

#

I think you just attach a t to the previous two solutions

red thistle
#

so then we'd have y=c1 y=c2e^(-4t) y=c1t and y=c2te^(-4t)?

#

would that last two be two different constants, however?

fathom flicker
#

I want to say yes, but also I am afraid I might not be leading us in the right direction

#

I don't want to confuse you or get you a wrong answer

red thistle
#

is there a way we can solve that IVP with wolfram?
if not i want to figure out something we can do with that way you showed me, but idk how to continue off where i left in the pic with blue ink

fathom flicker
#

I'll point out

#

,w y''''-8y'''+16y''=0

fathom flicker
#

if you can't tell from this

#

wolfram gives a weird answer

#

but

#

grouping constants

#

gives you

#

,, y=c_1e^{4x}x+c_2e^{4x}+c_3x+c_4

warm shaleBOT
#

AustinU

fathom flicker
#

and I can ^ explain how I got that if you need/want

#

and you can solve for those constants, based on the solution from wolfram

#

and the solution from wolfram

#

is so so close to what we were going to get

#

I don't understand why it is to the power of positive 4x

#

instead of -4x

#

otherwise that is what our solution was exactly

red thistle
#

to solve for the constants now

fathom flicker
#

just expand through their solution and group constants if you need to

#

To solve for the constants

#

the method will be

#

differentiate Wolfram's solution 3 times

red thistle
#

oh an then

fathom flicker
#

evaluate the derivatives and original solution at 0 (the initial values provided are all at x=0)

red thistle
#

do the, mk

fathom flicker
#

and then setup a system of equations

red thistle
#

i will try that rq

red thistle
#

oh crap thats upside down

fathom flicker
#

, rotate

warm shaleBOT
fathom flicker
#

, rotate

warm shaleBOT
red thistle
#

uhm

#

anyway

#

i need to recheck

fathom flicker
#

so uh, I personally can't really check that work for you without doing it all over again myself lol. I can tell you that if you used the method I detailed above that you will be able to solve the constants correctly

red thistle
#

i got the coeffs wrong, i need to go through again

fathom flicker
#

ah dang

#

btw

#

I am trying to figure out why wolfram is getting a positive exponent

#

so hopefully I'll get back to you with some news on that

red thistle
#

mk

#

unless i...

#

derivative of c1xe^(4x) is 4c1x^(4x)+c1e^(4x)

#

right?

#

unless i forgot the 4

fathom flicker
#

@red thistle

#

I figured out why I (or we?) had the signs swapped

#

the solution is e^(-at) for when the repeated roots are (r+a)^2

#

I assumed that it was for (r-a)^2

#

which is not the case

#

so that is why the signs for wolfram got swapped

#

the correct answer has positive exponents like wolfram says

red thistle
#

Alright, thats good

#

I went afk for a bit while i was trying to solve it

#

so im almost done with that

fathom flicker
#

nice

red thistle
#

imma need to commit that u(t) method to memory

#

and if i cant

#

just hope that i dont have to deal with higher order differentials like this on an exam

#

Thank you so much for your help, I was really bamboozled with this one

fathom flicker
#

yeah no problem

red thistle
#

its time for me to get to bed as its 1:30 in the morn, have a good one

#

.close

obtuse pebbleBOT
#
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obtuse pebbleBOT
#
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peak hamlet
obtuse pebbleBOT
peak hamlet
#

I don’t know how to do any of the question 4 questions

#

Like for example Q4 a.)

tired sierra
#

do you know how to derive

untold flax
#

differentiate using the chain rule

peak hamlet
#

Ok

fluid nymph
#

yes

peak hamlet
#

-(1-x^2)^-1/2

#

Sorry it should be -x in the front

#

I just realised

untold flax
#

ye

#

other than that it's correct though

peak hamlet
#

So what shall I do now?

untold flax
#

now plug in x= 1/2

#

for the gradient

#

and you're done

royal basin
untold flax
#

this is true

royal basin
#

you should not be conflating a function with its derivative

#

third line should begin with y' = or dy/dx = but not just = (which implies y =)

peak hamlet
#

Ohh yeah I was writing like that to be quicker

royal basin
#

do not

#

your fingers will not fall off from one extra second spent to write the symbols y and prime

peak hamlet
#

True, I’ll use full notation in the future

#

The answer is 1/2(1-1/4)^-1/2

#

I think

tired sierra
#

simplify it

peak hamlet
#

I think I did something wrong

#

(-3/8)^-1/2

tired sierra
#

no thats ok?

peak hamlet
#

Wait what

#

But how do I got further

tired sierra
#

wait -3/8

#

go through how you got -3/8

peak hamlet
tired sierra
#

you can't do that

peak hamlet
#

I did though

#

Why not?

tired sierra
#

because its still within the bracket

#

ok look at it like this

#

the -1/2 is a sqrt so

#

$-1/2-sqrt(3/4)$

#

ok that does nothing

#

uh hol horse

#

it would technically look like that

#

can you multiply -1/2 with 3/4?

peak hamlet
#

I think so

tired sierra
#

no you can't because its in a root

peak hamlet
#

Oh yeah

#

You’re right

tired sierra
#

so redo that

peak hamlet
#

So that would be the answer

tired sierra
#

... has your teacher not taught you this?

peak hamlet
#

Wait no that is not the answer

peak hamlet
tired sierra
#

ok so whatever x is

#

that is the gradient of the tangent

peak hamlet
#

Ok

#

But from where we are right now how do we get to finding its value?

tired sierra
#

wait did you sub in -1/2 or 1/2

peak hamlet
#

1/2

tired sierra
#

ah kk

#

so most of the time for me it'd give me a whole number or like a fraction

#

but do they want it in a decimal or exact form?

#

because you can kinda leave it like that if you want it in exact form or turn it into a decimal

peak hamlet
#

The answer is a fraction

#

-(1/squareroot 3)

#

According to my textbook

tired sierra
#

ok give me a minute

#

ok I got it

#

so our answer is right

#

now we just simplify

#

-1/2 / sqrt3/4

#

ok?

#

then we reciprocal sqrt 3/4 so we can get

#

sqrt 4/3

peak hamlet
#

Ohhh

tired sierra
#

since sqrt 4 is 2

#

= 2/sqrt3

#

so -1/2 * 2/sqrt3

#

and I think you can do the rest

peak hamlet
#

Yes

#

Thank you very much I just got the answer

#

.close

obtuse pebbleBOT
#
Channel closed

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obtuse pebbleBOT
#
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raven portal
obtuse pebbleBOT
raven portal
#

Can someone help me with this

knotty crow
#

it's not clear

raven portal
#

what do you mean

knotty crow
#

is base 1 + sqrt(2)?

raven portal
#

no

knotty crow
#

so it's denom?

raven portal
#

no the (1+2) is the base

knotty crow
#

so it's just 3, right?

raven portal
#

no

#

(1+root of 2)

knotty crow
#

when I asked you said it wasn't the base

#

but nvm

#

okay

raven portal
#

oh my bad

knotty crow
#

what is the number we take log of?

raven portal
#

ohhh i forgot to change it

#

3+2sqrt(2)

knotty crow
#

and some power there?

raven portal
#

3

knotty crow
#

okay, now we can do it

warm shaleBOT
raven portal
#

my bad i forgot to translate the numbers

knotty crow
#

firstly I'd expand (3 + 2sqrt(2)) ^3

#

o no

#

notice that (1+sqrt(2))^2 = 3 + 2sqrt(2)

#

so it becomes

warm shaleBOT
knotty crow
#

and I guess you can proceed from here

raven portal
#

yeah the answer is 6

#

but i kinda didnt undestand

warm shaleBOT
raven portal
#

why 1+sqrt(2)^2 tho

#

sorry my math is bad

knotty crow
#

use formula (a+b)^2 = a^2 + 2ab + b^2

#

to expand that

raven portal
#

oh

#

so at first we xpand the (3+2sqrt(2))

knotty crow
#

no, we do (1+sqrt(2))^2

#

(we want to show it is equal to 3 + 2sqrt(2))

raven portal
#

ok

#

is there any other way to solve this question?

#

i think i would understand better if u show it step by step if you dont mind

#

can i ask another question?

knotty crow
#

ye

raven portal
#

What's this

knotty crow
#

find 'a' firstly, then subtitute it into 4a+1

raven portal
#

2^3/2 ithink

#

oh

knotty crow
#

that's 2sqrt(2)

#

yeah

raven portal
#

yeah

warm shaleBOT
raven portal
#

Yeag

knotty crow
#

now notice that 4^a = 2^(2a) and compare exponents or apply logs

raven portal
#

So its 4^2^3/2 + 1 right?

#

Oh my bad

#

So a is 3/4

knotty crow
#

yea

raven portal
#

So 4×3/4+1 right?

#

And that would be 4

knotty crow
#

right

raven portal
#

And i forgot to add at the end of the questions it says with the base of 4

#

Soo 4^4?

knotty crow
#

rather 4^1 = 4

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for 4a + 1 obv

raven portal
#

Answer is 1 nice

#

But i still don't understand the first question

#

why we say they are equal

raven portal
#

What about this

#

Sqrt(8) and 4 are base

#

I thought the answer was 7/12 but it wasn't

#

Aren't we supposed to to make the power of. Base upside down

#

<@&286206848099549185> sorry

#

i think i should make a new one

#

.close

obtuse pebbleBOT
#
Channel closed

Closed by @raven portal

Use .reopen if this was a mistake.

nocturne dove
#

.reopen

obtuse pebbleBOT
#

raven portal
#

.reopen

#

huh?

#

did i do something wrong?

high lily
#

show work

raven portal
#

what?

high lily
#

I thought the answer was 7/12 but it wasn't
show all your work leading to that value

raven portal
#

ok let me write them in english

grizzled pagoda
#

1/4 + 2/3

#

will be 11/12

raven portal
#

ohhhh

#

im so dumb

#

why did i do this

#

ok

#

i have two other questions

raven portal
#

And this

high lily
#

did you copy down the question correctly

raven portal
#

yeah

grizzled pagoda
# raven portal

From your second eqn (with log)
Use the sum rule, find relation between x and y. ||you get x=2y||
Then substitute back in the first eqn, take 2^y as another variable and solve for cubic... but uh i think it wud end up in non real roots...

raven portal
#

the answer is 4/5

high lily
#

,w 2^(4/5) +8^(2/5)

high lily
#

doesn't sound right

raven portal
#

hmmm ny math teacher kinda speed runed this part so

#

idk how to solve it

#

but he said the answer is 4/5

sweet edge
#

teachers can make mistakes too

raven portal
raven portal
#

iknow this is basic log im just dumb

#

what hould i do

obtuse pebbleBOT
#

@raven portal Has your question been resolved?

raven portal
#

yeah i can make another one

#

yeah

obtuse pebbleBOT
#
Channel closed

Closed by @raven portal

Use .reopen if this was a mistake.

obtuse pebbleBOT
#
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Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

edgy acorn
#

hello, how do you solve this integral without using the reduction formula? instead i'm supposed to reduce the power by using integration by parts.

median dome
#

what do you mean by the reduction formula?

edgy acorn
#

so you're not allowed to memorize that formula, then plug in, instead you need to get to the reduction formula solution by integrating by parts, so you kind of are still using it.

median dome
#

how would you do it by integration by parts?

edgy acorn
#

if you were to write a proof on the reduction formula, it would involve integration by parts. But I don't know how to do it

median dome
#

have you learned this formula in your class/course?

edgy acorn
#

no

median dome
#

well

#

you should use trig sub for this anyway

#

but idk about the reduction formula i have never come across it

edgy acorn
#

he won't let us use trig sub either opencry

#

it's np

#

.close

obtuse pebbleBOT
#
Channel closed

Closed by @edgy acorn

Use .reopen if this was a mistake.

edgy acorn
#

bad luck on the prof I guess

obtuse pebbleBOT
#
Available help channel!

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Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

floral canopy
#

Yo I have a question.
Which set is [2, 3, 4) ∩ ℤ

floral canopy
#

like what does this [) mean

kind hawk
#

half open interval

#

no wait

#

that would be if it didnt include the 3

#

[2,4)

#

uhm

#

not common notation

floral canopy
#

what if the 4 wasnt there

#

was it just [2]

kind hawk
#

that would just be {2}

floral canopy
#

but why

#

oh I get it

#

tysm

#

.close

obtuse pebbleBOT
#
Channel closed

Closed by @floral canopy

Use .reopen if this was a mistake.

kind hawk
#

you should look up where that notation is defined in your book

#

it could also be that [2] = {1,2}

obtuse pebbleBOT
#
Available help channel!

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Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

raven portal
#

hi

obtuse pebbleBOT
royal shard
#

hello^^

raven portal
royal shard
#

let me decifer it haha

#

$log_{y}x=1/\mu$

warm shaleBOT
#

~Martin

raven portal
#

where did that p came frpm

royal shard
#

looks like you didnt write mu, but i dont know how to write that weird letter haha

#

which p?

raven portal
#

p idk how write it

heavy depot
#

$\mu$

raven portal
#

3.14

royal shard
#

ah

warm shaleBOT
#

CrEpasPmkinPie

heavy depot
#

that?

raven portal
#

thre isnt any p

#

its not p

royal shard
#

i dont know how to write this in latex so i used mu

raven portal
#

its 3

heavy depot
#

pi

raven portal
#

3

#

i forgot to change to 3