#help-4

1 messages · Page 23 of 1

haughty jackal
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YEAH

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I GET IT

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So, it's (2 * 8 - 1) ways?

graceful zinc
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yea

haughty jackal
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Then from Case 1, number of matrices is (2 * 8 - 1)² ways, right?

graceful zinc
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yes

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think similarly for case 2

haughty jackal
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Mm

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Brb

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Okay

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[2(7²) - 7] ways?

graceful zinc
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yea

haughty jackal
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,ask 8⁴ - (15² + 2 * 49 - 7)

haughty jackal
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Yeah

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Thank you

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.close

vale dockBOT
#
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formal veldt
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I have a weird question. Is it possible to put smaller exponential equations that follow one big exponential equation? Kind like this:

neat locust
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You could do a piecewise function i suppose

formal veldt
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I would like to keep it as one equation

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I'm making a game and I need the enemy health to grow exponentially, but as your playing it also goes through a cycle of getting harder and easier.

mild marsh
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you could always cycle between increasing at two different exponetial rates

lyric sundial
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It's not exponential but the behaviour is similar

formal veldt
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yeah

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if only there was a way to make it exponential it would work

lyric sundial
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Or e^that

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$$f(x) = e^{x−\abs{\sin(x)}}$$

rocky lotusBOT
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Alberto Z.

lyric sundial
wicked zenith
lyric sundial
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Yes

formal veldt
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that does work

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how could I slow it down a bit

lyric sundial
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Instead of e you can pick a smaller number, like 2 or 1.3

wicked zenith
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pick integral points allong your main exponential, then between pairs construct another exponential passing through both points whose derivative is flat at the first.

lyric sundial
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If I've understood correctly

formal veldt
knotty storm
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judging by ur name and by ur question, is this for some sort of car game?

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like shifting gears n stuff

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@formal veldt

formal veldt
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Zombie game

knotty storm
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ah ok

lyric sundial
lyric sundial
# lyric sundial

Here's the graph for 4 different values of the base.

blue → e
green → 2
orange → 1.7
red → 1.3

vale dockBOT
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@formal veldt Has your question been resolved?

wicked zenith
vale dockBOT
#
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north scarab
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@cloud coral Sorry, I had something sudden come up

north scarab
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what were you saying?

north scarab
stark wedge
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mark the angles on the diagram.

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the question says angle BAC is 42° and angle ABC is 68°.

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can you mark these on the diagram?

north scarab
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@stark wedge

stark wedge
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indeed

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can you mark any other angles on here?

north scarab
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Yes let me write it

stark wedge
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ok those won't help you a whole lot

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how about angles ACD and DCB

north scarab
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one sec someone called me suddenly

north scarab
stark wedge
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what do the angles in any triangle add up to?

north scarab
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180

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ok triangle ACD is 180-90-42

stark wedge
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one place

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angle ACD is 180 - 90 - 42 yes.

north scarab
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yep

stark wedge
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here is a slightly more polished diagram

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you also know AB = 50m

north scarab
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yep

stark wedge
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now you'll have to do some right-triangle trigonometry in triangles ACD and BCD

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would you like to try it yourself or do you want more explicit instructions

north scarab
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ill try

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solving from here

stark wedge
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k

north scarab
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first of all what is the

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question even asking

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the a) part

stark wedge
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it's asking you to prove that w*(tan(48°) + tan(22°)) = 50

north scarab
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so

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i think I need to solve

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for w?

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to answer this question

stark wedge
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not quite

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in fact almost the opposite

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solving this question would be a step on the way to finding the value of w

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no, here's what you should do instead:

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express AD and DB in terms of w

north scarab
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Ill try n solve it rn

vale dockBOT
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@north scarab Has your question been resolved?

vale dockBOT
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merry jasper
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Im confused why on the chatgpt, it didn't use the first equation. I don't understand

stark wedge
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!nogpt

vale dockBOT
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Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).

merry jasper
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Why do you use the middle piece for the left hand limit

stark wedge
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also show the original problem please?

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i think there might be some misreads going on regarding which limits exactly you might be asked to find

merry jasper
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We don't need to graph we just find the limits

stark wedge
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i wasn't talking about graphing

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you miswrote (a)

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(a) is $x \to -2^+$

rocky lotusBOT
stark wedge
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i.e. you're approaching -2 from the right

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that means you're in the middle subdomain i.e. -2 ≤ x ≤ 2

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thats why you use the middle piece for it

merry jasper
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So for the left hand limit, we use the middle piece because its the closest to the as x approaches -2?

stark wedge
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this is not left hand

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this is right hand

merry jasper
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Which equation do I use for the left hand limit

stark wedge
stark wedge
merry jasper
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-2

merry jasper
# stark wedge

ohh so the middle piece is in between -2 and positive 2

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cause im struggling to understand what's the step by step to get the limits and if its continuous

stark wedge
merry jasper
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My bad, I misunderstood it cause I thought its x=-2

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So this is the limit for -2

stark wedge
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no you mixed it up

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completely, actually, by the looks of it

merry jasper
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sorry, so how do I find the limit of -2

stark wedge
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at -2

merry jasper
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it was already right, since my first answer was dne

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since 2 and 0 are not =

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instead of using the last one, i shouldve used the middle piece

merry jasper
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is that correct

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and greater than -2 approaches it from the left

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so this is for the limit at positive 2?

stark wedge
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you don't say "limit of [number]", you say "limit at [number]"

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or more accurately "limit of [function] at [number]"

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but yes, you worked out the limit of f(x) at 2 correctly now

merry jasper
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alright thanks, i understood it more with the number line

safe vector
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Where's the question

merry jasper
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they didn't teach that at school, which is odd

stark wedge
# merry jasper

@safe vector here, but we have resolved it already by the looks of it

stark wedge
merry jasper
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thanks very much, i understand it now

safe vector
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Oh yeah it's x tends to [number]

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@merry jasper let me ask you a simple stuff

merry jasper
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sure

safe vector
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Why 1^∞

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Indeterminent

merry jasper
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because it has no limits?

safe vector
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?

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No

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I mean why you can't write 1^∞ as 1

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Let me tell you

stark wedge
safe vector
merry jasper
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its all good dw, i dont mind

safe vector
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1^∞ isn't 1 because the 1 written there means that it "TENDS" to 1

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It's not actually correct 1

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It's tend to 1

merry jasper
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what does it mean by like tends to 1

safe vector
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Like 1.0000000000001

stark wedge
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you're explaining it wrong.

safe vector
safe vector
stark wedge
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$1^{\infty}$ is shorthand for a function in the form $f(x)^{g(x)}$ where $\lim f(x) = 1$ and $\lim g(x) = \infty$.

rocky lotusBOT
stark wedge
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any talk of indeterminate forms fundamentally deals with functions not simply numbers.

safe vector
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ABSOLUTELY DUMB

stark wedge
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...

stark wedge
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HEY MAYBE TONE IT DOWN WITH THE CAPSLOCK WILL YOU.

safe vector
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the function you meant is NOT 1

merry jasper
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wait what's g of x

stark wedge
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g(x) is another function

safe vector
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F(x) is not exactly 1

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Its near to 1

stark wedge
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i specifically said the limit of f(x) is 1.

safe vector
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Thats what I was explaining

stark wedge
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i never said f(x) was constant 1

merry jasper
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ohh so thats what he means by 1.00001

stark wedge
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but your explanation of "a number not 1 but close to it" is very misleading

safe vector
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Then how am I wrong 💀

stark wedge
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you're misleading that's how

merry jasper
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yeah i was kinda confused cause i thought u meant it was 0.99

stark wedge
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see?

merry jasper
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cause you said close to it

safe vector
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The function is either 1+ or 1-

safe vector
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You are new to calculus ig

merry jasper
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not really dumb, just wrong sentence

merry jasper
safe vector
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Explaining you with functions would mess it up for you

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Since you are new

merry jasper
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we're about to um, discuss the graphing of the functions i sent here. so we're just asked to answer for the limits

safe vector
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Oh cool

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Is the question solved?

merry jasper
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i just got confused by the step by step of it, until ann showed me the number line

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yeah

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so like one more thing

safe vector
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Alr you could close it now

safe vector
merry jasper
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for example this one

safe vector
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Piece wise functions

merry jasper
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how would i start it, like do i find the limites at -1

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of right and left hand

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wait let me try and solve it and see if its correct

safe vector
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I mean that is what piece wise functions do

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In "a" you could see that we have to approach -1 from right side

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So we use -x² + 1

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Answer to "a" is 0

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In "b" we approach -1 from left side

merry jasper
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wait so this is correct

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cause 1 approaches from the left

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and x^2+1 approaches from the right

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at the number line

merry jasper
safe vector
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Check "c" part

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That's correct

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I thought you didn't solved "c" lol

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All are correct

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Wait

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You did "a" wrong

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The answer is 0

merry jasper
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wait wym by a and c

safe vector
safe vector
merry jasper
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OH yeah its -1

safe vector
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A

merry jasper
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wait no its 1

safe vector
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The answer is 0

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Guess you thought -x² = 1 💀

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It's -1

merry jasper
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oh yeah i forgot the integer of x^2

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its still dne right cause

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both limits are not equal

safe vector
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What are you saying, im talking about "a" partt

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"c" part is already correct

safe vector
merry jasper
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Ohhhh

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im sorry, i didn't notice it was given in the book

safe vector
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Yeah 🥲

merry jasper
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yeah i didn't put -x^2

safe vector
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Yeah

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So answer to "a" part is 0

merry jasper
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yeah

safe vector
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Anything else?

merry jasper
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all good, i understand it now. I just got confused cause they only taught us how to solve one limits

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thanks

safe vector
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!close

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use ".close"

merry jasper
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.close

vale dockBOT
#
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safe vector
vale dockBOT
safe vector
#

Question 13

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Is it getting done from LH rule?

stark wedge
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,rccw

rocky lotusBOT
stark wedge
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LH is only for masochists here

safe vector
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Nah it's possible

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Can't find other way

stark wedge
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i didn't say it was impossible, just that it is very painful and unpleasant

safe vector
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Let's try

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You continue with your method

hollow shuttle
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my gut feeling is that there's some closed form for that product of roots

safe vector
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My gut feeling really said LH

hollow shuttle
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wait hold on

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i remember this question

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i think we have the same course material lmao

safe vector
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Loll

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Cengage?

hollow shuttle
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nope

safe vector
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Oh

hollow shuttle
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it might be taken from there though,

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i'm also in a jee course

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anyway i'll try using LH because it actually seems like it might work

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unless i have to do it twice

safe vector
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Something like this

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I mean we can take natural log

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Idk

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@stark wedge

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Found a way?

stark wedge
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your x's don't look like x's...

safe vector
stark wedge
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i did it with series expansion

safe vector
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Ain't that big

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That would be so long ig

stark wedge
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$\prod_{k=2}^n \cos(kx)^{1/k} = \prod_{k=2}^n (1 - 2 \sin^2(kx/2))^{1/k} = 1 - \sum_{k=2}^n \frac{2}{k} \paren{\frac{kx}{2}}^2 + O(x^4)$

rocky lotusBOT
safe vector
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Mhm

stark wedge
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some dust will need to settle but the idea is that you only need the x^2 term

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you're gonna need to do some algebraic shuffling around

safe vector
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Wait let me try more

stark wedge
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which i realize now i messed up in my work so i do not have anything checkable

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however i can tell you for sure this will cook

safe vector
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Ikr

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Advanced mathematics 💀

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Does this work?

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I took natural log both sides

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Now we can try differentiation

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But idl

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Idk*

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@stark wedge found a way?

stark wedge
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sorry i am busy now

safe vector
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🥲

sterile gust
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ur on the right track

safe vector
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I messed up

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Gotta try another approach

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I wonder if there a result for this series

sterile gust
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a hint would be writing $P(x) = \prod_{x=2}^n ( \cos (kx))^{\frac 1k}$

rocky lotusBOT
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whiteboard

safe vector
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Why you giving hints

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Just solve it and explain 😭

sterile gust
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no im not gonna solve it.

safe vector
safe vector
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Ann also wrote it

sterile gust
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as i said ur on the right track.

safe vector
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Okay 🥲

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Wait what

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Is it tanrx?

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But then you can't observe pattern after y hops

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@@hollow shuttle

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<@&286206848099549185>

nocturne sable
hollow shuttle
#

holy hell it's the astronomy guy

hollow shuttle
safe vector
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🥲

hollow shuttle
safe vector
#

Oh what let me check

nocturne sable
safe vector
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Im trying wat

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Wait*

hollow shuttle
safe vector
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Oh bro

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Tanrx/2x

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Is giving a pattern maybe

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I got the same result

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!!

hollow shuttle
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awesome

safe vector
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It was 1/2 × 1+2+3+4....+n

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Now what

hollow shuttle
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the question says that expression is equal to 10

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so just solve for n

safe vector
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Oh ye

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Wait

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Let solve

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Le me solve

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6 is the answer ig

hollow shuttle
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yep

safe vector
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Is it correct?

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100%?

hollow shuttle
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should be

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it's pretty unlikely if we both got the same wrong answer

safe vector
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Alr

safe vector
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I used LH

hollow shuttle
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yeah i used ann's expansion

safe vector
#

Betting on a pattern was brilliant by me ig 💀

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Alr ty

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woven forge
#

we know from linear algebra that if a linear system contains more unknowns than equations, then the system has infinite solutions, that can be expressed as a parameterization of the free variables. but what if the system has more equations than unknowns?

stark wedge
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it could be any of the three

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it could have infinitely many solutions (if it collapses enough)

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it could have a unique solution

viscid spade
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depends if the left over equations are verified or not

stark wedge
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or it could not have any sols at all

stark wedge
woven forge
#

if for instance we have 3 linear equations that are linearly independent in R^2 then the system if it did have a solution, should have only one soltion right?

viscid spade
#

can we have a picture of the problem ?

woven forge
#

.close

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midnight pier
#

can someone please help me analyse what the graph is trying to say especially wrt the second statement

glass kelp
#

intensity of radiation vs wavelength

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this is from uhh

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rayleign-jeans law

midnight pier
glass kelp
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vs max's distribution

midnight pier
#

what does it say

glass kelp
#

classical physics predict infintie intensity while experimental results say the intensity drops after a certain wavelength

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u should look into

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the uhh

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"ultraviolet catastrophe"

midnight pier
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okay, will that help me undersatnd this?

glass kelp
#

yes

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i think so

midnight pier
#

okay!

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i will!

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thank you so much!

#

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jovial edge
#

What have you tried?

somber sequoia
#

just value of p?

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there's no other conditions?

lost marlin
#

!xy

vale dockBOT
#

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

jovial edge
#

Ohh yeah, that's odd

upper island
#

What is the conditions for a/b=0 ?

vale dockBOT
#

@twilit plume Has your question been resolved?

twilit plume
#

i think the problem is wrong 😭

upper island
#

Why ?

twilit plume
#

idk

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nvm i got it guys

#

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fast sentinel
#

"Let S={v_1,...,v_k} be a set of vectors of the vector space V, n<k
a) we can obtain a vector basis by eliminating vectors of S
b)S is a generating system, but not a vector basis, because there's more than n vectors
c) it can be V=L(v_1,...,v_n)+L(v_n+1,...,v_k)"

I think the one that's true is b) because for S to be a vector basis of V it has to be a set of linearly independent vectors of V and if S were to be linearly independent, some vector necessarily would have to be outside of V, because there are more vectors in S than dim(V). But I'm not entirely sure. Please help

ruby sleet
#

or is

Let S={v_1,...,v_k} be a set of vectors of the vector space V, n<k
all the assumptions we have

fast sentinel
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No, just a set of vectors of V

ruby sleet
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ok

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so when you have more vectors than the dimension of V, you must have a generating system?

fast sentinel
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Necessarily no, because it could be the multiples of one vector of V

ruby sleet
#

yes for example

fast sentinel
#

Like say if I have S={(1,0),(2,0),(3,0)}, S is a set of vectors of R² but you can't obtain a vector basis of R² nor it is a generating space of R² and R² is not a linear combination of anything combination of vectors of S.

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So hold on

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The one that's true is c. Because ot doesn't impose for it to be a basis and uses the keyword "can"

ruby sleet
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it IS possible that V = Span(v_1,...,v_n) + Span(v_(n+1),...,v_k)

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though I'm wondering if it's just meant to be a "+"

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or an $\oplus$

rocky lotusBOT
#

Raphaelisius Maximus MMIII

ruby sleet
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both would technically be possible

fast sentinel
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It's not a direct sum

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Just sum

ruby sleet
#

ok

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well just take v_1,...,v_n a basis of V

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and v_(n+1)...v_k whatever you want

fast sentinel
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Sure S={(1,0),(0,1),(1,1)}

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And V = R²

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But like the question is about any set and any vector space so each statement has to be true for it to be correct since I found a set that doesn't work for a) and b) then c) has to be the correct one

vale dockBOT
#

@fast sentinel Has your question been resolved?

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umbral flare
#

hey can someone walk me through this

vale dockBOT
umbral flare
#

using de moivres theorem
present cos^5 x in terms of multiple angles

#

idk what to do like at all

viscid spade
#

use the euler's formula !

umbral flare
#

i tried using
2cosx = z + z^-1
but that kinda just circled back around

safe fulcrum
umbral flare
#

uhhh is there a way to do it without using the exponential forms

#

bc in my textbook i havent gotten to the exponential stuff yet and this exercise is right before it

safe fulcrum
#

e^(5ix) = cos(5x) + i sin(5x) by Euler's identity

viscid spade
#

¯_(ツ)_/¯

umbral flare
#

idk this is supposed to be like one of the final exercises on pure de moivres

#

i think what sort of worked but also didnt was getting cos^5 x in terms of other powers

#

where i got

#

cos^5 x = cos5x + 10cos^3 x sin^2 x - 5 cosx sin^4 x

#

my textbook answer is
cos^5 x = 1/16(cos5x + 5cos3x + 10cosx)

#

idk... power reduction? somehow?

safe fulcrum
#

it'd help if you could show your work on paper

#

then upload a photo

#

or if you know how to use LaTeX use that

umbral flare
#

1 sec

#

ive no idea what im doing but o well

safe fulcrum
#

yeah then the line where you write $\cos(5 \theta) = \cdots$ is good

#

then you have to replac $\sin^2 \theta = 1 - \cos^2 \theta$ I think

rocky lotusBOT
safe fulcrum
#

hmmm let me think

#

ahhh right

#

you have to use that $z + \frac{1}{z} = 2 \cos \theta$ instead

umbral flare
#

yeah i was guessing that but idk

rocky lotusBOT
umbral flare
#

oof

safe fulcrum
#

then you can raise both sides to the power of 5

umbral flare
#

yeah but then like

#

wait

#

ok

#

lemme try this

#

ok i think this is gonnawork

#

im basically expanding the

#

(z + z^-1)^5

safe fulcrum
#

yep

umbral flare
#

using pascals

#

and then ill just convert it to regular multiple angles

#

and take the real part

#

okay thats it then

#

thanks for helping out

safe fulcrum
#

for example, $z^3 + z^{-3} = (\cos 3 \theta + i \sin 3 \theta) + (\cos 3 \theta - i \sin 3 \theta)$

rocky lotusBOT
safe fulcrum
#

that's the idea

#

no worries!

umbral flare
#

yup

#

tysm

#

bai

safe fulcrum
#

bye

umbral flare
#

.close

vale dockBOT
#
Channel closed

Closed by @umbral flare

Use .reopen if this was a mistake.

#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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coarse aspen
#

Hello

vale dockBOT
coarse aspen
#

So what times does: 20x75^x get multiplied with to because 300x75^x

glass kelp
#

holy notation

#

[ 20 \times 75^x]

tidal swift
#

isn't this a ratio

glass kelp
#

the first one is this, right?

coarse aspen
#

Naur wait I meant uh

rocky lotusBOT
glass kelp
#

this?

coarse aspen
#

YEAH

tidal swift
#

if this is what you meant

#

you know both numbers have a 75^x

glass kelp
#

divide ${300 \times 75^x}$ by ${20 \times 75^x}$

rocky lotusBOT
tidal swift
#

what if you replace both 75^x by the word something

glass kelp
#

and u shall have ur answer

tidal swift
#

can you do it?

coarse aspen
#

Can 75^x be divided

#

D:

glass kelp
tidal swift
#

yes, why not

coarse aspen
#

So id say my answer is 15

tidal swift
#

there you go

coarse aspen
#

YAY

#

THANKSSS sorry my math teacher didn't have time to help so I just grabbed my phone

tidal swift
#

whenever you're confused and you see two equal numbers being compared

#

just replace those equal numbers with something else

#

for example

coarse aspen
#

Okayy

tidal swift
#

if you were asked for the ratio between 20(8923749802374) and 300(8923749802374)

glass kelp
#

here how i got this. let ${a}$ be ur answer. then ${a \times (20 \times 75^x) = 300 \times 75^x}$. divide both sides by ${20 \times 75^x}$ gives u ${a}$. 😄

tidal swift
#

you can just abstract that bunch of numbers as "something"

coarse aspen
#

Okay okat

tidal swift
#

then you have 20 times something vs 300 times something

rocky lotusBOT
tidal swift
#

then it would be pretty easy from there

coarse aspen
#

THANKSS ima get back to doing math now❤️❤️

#

How do I end the conversation?

#

Close

glass kelp
#

.close

vale dockBOT
#
Channel closed

Closed by @glass kelp

Use .reopen if this was a mistake.

coarse aspen
#

.close

vale dockBOT
#
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earnest ingot
vale dockBOT
earnest ingot
#

I think I'm having a brain fart

silk wasp
#

yooo wsgg people

#

help me get better at math

smoky lily
vale dockBOT
silk wasp
#

oh mb

earnest ingot
#

nvm I figured out my mistake lol

#

.close

vale dockBOT
#
Channel closed

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silk wasp
#

its a comlicated server

ivory valley
earnest ingot
#

Yes it's permutation groups

vale dockBOT
#
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undone dew
#

Hello. The square root only has one value, right? My teacher says it has two values.

main sundial
#

there are two values

#

a square root can be positive or negative

#

thus two values

marble furnace
#

It can only give positive values

marble furnace
undone dew
marble furnace
#

it's different from x= √9

main sundial
#

depends on what you are solving for

marble furnace
stark wedge
#

6|x| is correct as-is, but can you show us the entire page?

#

i think there might be something extra that you're not showing us

undone dew
hot tide
#

,rccw

rocky lotusBOT
tidal swift
#

i think if a square root is given to you without you having to rearrange for it, it is likely referring to the principal root (the positive answer)
but it depends on context too

stark wedge
#

hmmmm

#

see i was thinking there would be something at the top of the page which says "treat all letters as positive"

#

but i dont see anything like that

tidal swift
#

wait now that you mention it

#

the page starts at question 3

#

i don't think this is the start of the whole paper

#

@undone dew OP, are there any more instructions on the first page?

undone dew
undone dew
tidal swift
#

so this entire practice paper is about rationalization?

undone dew
#

Yes

tidal swift
#

not sure what there is to rationalize in questions like this unless exponent rules are also used

#

but yes, in exercises like this, generally (and keyword: generally) they want the principal/positive root

undone dew
#

Aah, yes, It also includes the exponentiation rules that we saw in the past class.

tidal swift
#

though technically speaking, a square root does have two solutions, but only if you rearranged a square into a square root yourself

#

if you are given a square root directly, it is almost always the positive root unless there's some instruction saying otherwise

undone dew
#

I understand

#

Thanks

tidal swift
#

nps

undone dew
#

.close

vale dockBOT
#
Channel closed

Closed by @undone dew

Use .reopen if this was a mistake.

vale dockBOT
#
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ebon thorn
#

Are we just testing for some c value that works or doesn't work here?

stark wedge
#

some f and some c.

ebon thorn
#

If I wanted my f to be x

#

So, f(x) = x

stark wedge
#

i mean... that won't work as a CE of the kind they're asking for.

#

actually wait.

#

there are two parts to this.

ebon thorn
#

Then we would have to ensure that the lim for this implies the existence or not?

stark wedge
#

counterexample

#

(a) show that if f is differentiable then that limit exists an is equal to c
(b) show that the limit can exist without f'(c) existing

#

which one are you trying to do rn

ebon thorn
#

For part (a), that is just plugging and chugging into the limit formular of f(x) - f(c)/ (x - c) = f'(c)

#

You get the exact same equation they have

#

Now, that should suffice for this to be differentiable.

#

Now, I am on the second part of showing a counterexample.

stark wedge
#

ok

#

you missed some brackets there but whatever.

#

part (b) is about pretending you're malicious and deliberately constructing a function so that the given limit exists without f being differentiable.

#

im gonna make your life a bit easier and say you should concretize to c=0 and f(0)=0

#

that way you're tasked with defining your function in such a way that lim nf(1/n) exists but f is not differentiable at 0

#

perhaps f need not even really be continuous at 0

ebon thorn
#

So, f = (1/x)?

stark wedge
#

dunno what that's supposed to mean

#

do you mean f(x) = 1/x

ebon thorn
#

Yeah

stark wedge
#

ok can you tell me what the expression n*f(1/n) simplifies to for this f

ebon thorn
#

n*(n) = n^2

stark wedge
#

and does its limit as n->infty exist?

ebon thorn
#

No

stark wedge
#

so does that work as a counterexample?

ebon thorn
#

Well, yes, it goes to infinity

#

It diverges

stark wedge
#

in this problem i am 100% sure "exists" means "exists and is finite"

ebon thorn
#

And needs to be finite?

stark wedge
#

indeed, f(x) = 1/x won't cut it.

ebon thorn
#

We would use f(x) = x

stark wedge
#

back to the drawing board.

#

f(x)=x doesn't work because f'(0) exists.

ebon thorn
#

n * 1/n = 1

stark wedge
#

f(x)=x doesn't work because f'(0) exists.

#

let me repeat myself \

#

defining your function in such a way that lim nf(1/n) exists but f is not differentiable at 0

#

you want the following two things to both be true at the same time:

  1. lim n*f(1/n) exists
  2. f'(0) does not exist
ebon thorn
#

It says in the problem that the existence of the limit of this sequence doesn't imply the existence of f'(c)

#

Oh, we choose c = 0

#

Well, fuck. Give me 50 Intellectual Quotient points and I could figure it out

stark wedge
#

i do not think this is about any intelligence points or whatever

#

unless your INT stat affects your reading comprehension

ebon thorn
#

Where am I supposed to pull out the high genius move to come up with a function that would give us a limit?

turbid valve
ebon thorn
turbid valve
#

[a character in a campaign I'm in severely struggled due to their INT getting wacked down to 1, which had that effect among others]

ebon thorn
#

Dude. Fuck off. YOu are derailling

stark wedge
#

calm your tits lol

turbid valve
#

Point is, we've so far boiled this down to
"find a function f such that

  • f(0) = 0
  • this limit exists
  • f'(0) doesn't exist"
stark wedge
#

so just think about a sequence

#

a_n

#

such that the limit of n a_n exists and isn't 0

#

and then define your function to be f(x) = a_n if x=1/n; 0 otherwise

ebon thorn
#

I am thinking of a piecewise function

#

How about f(x) = x^2 + x

#

This won't give us f'(0) = 0

turbid valve
#

But f'(0) exists there

ebon thorn
#

Oh, f'(0) shouldn't exist

turbid valve
#

We're not bothered about what f'(0) equals, just whether it exists

stark wedge
ebon thorn
#

f(x) = 1/x

ebon thorn
stark wedge
#

and also it is as if you aren't reading my msgs

ruby sleet
stark wedge
#

or you are and then they escape you

glass kelp
turbid valve
ebon thorn
#

Okay, let's take it back from the beginning

#

Too many cooks in the kitchen. Dman

turbid valve
#

...I was kinda waiting you were going to take it to the beginning...

ebon thorn
#

Welp, I have no idea

#

Okay, give it to me genius. Use that high intellect of yours to pull something off with your god-given intuition

turbid valve
#

Now, someone did give it to you not more than 10 mins ago:

ebon thorn
#

So, the piecewise if f(x) = a_n?

#

if x_n, 0 otherwise

stark wedge
#

you fumbled it

turbid valve
#

You're getting hung up on the word "piecewise"

stark wedge
#

what is "x_n" 💔

turbid valve
#

Forget about it

ebon thorn
#

Honestly, moving on.

turbid valve
#

You want a function f, such that
f(x) = a_n (i.e. the nth term in some sequence) if x = 1/n for some natural number n
and f(x) = 0 otherwise (i.e. x is not 1/n for any natural number n)

ebon thorn
#

So, how does this give us what we need?

turbid valve
#

Further, you want the sequence $(n a_n) _{n\ge1}$ to have a limit

rocky lotusBOT
#

Waes (Wires)

ebon thorn
#

I am confused. What is even going on anymore

turbid valve
ebon thorn
#

Yes

turbid valve
#

Do you understand what the question is asking you, first of all?

ebon thorn
#

It merely says to give a counterexample for why the limit from part one couldn't work.

#

What qualifies has not being differentiable?

#

It is a constant, right?

turbid valve
#

"couldn't work" in doing what?

ebon thorn
#

Be differentiable

turbid valve
#

Why "limit exists" doesn't imply "derivative at that point exists", that is correct

#

Okay, so

#

We're doing some things to simplify the work involved

#

Number 1:

#

Let's let c be 0

#

Then that f(c + 1/n) thing, we can just treat as f(1/n)

#

Number 2:

#

Let f(c) = f(0) be 0

#

Then that limit that we're assuming exists is just
lim n f(1/n)

ebon thorn
#

This f(1/n) = a_n where x = 1/n and 0 otherwise?

#

In order for f'(0) to not exist?

turbid valve
#

That's our goal, yeah

#

We're explicitly trying to find (read "build") a function f so that the limit exists, but that f'(0) doesn't

glass kelp
#

i have another idea: we can view the above limit as right derivative by considering u = 1/n pandathink

turbid valve
turbid valve
#

[I guess it could? again, a little too tired to check this]

ebon thorn
#

Real Analysis is Real Ass

glass kelp
#

im gonna try my approach then

ebon thorn
#

Because this course is garbage

glass kelp
#

Consider ${h = 1/n}$, as ${n \to \infty}$, ${h \to 0^+}$
[ \lim_{n \to \infty} n\left(f\left(c + \frac{1}{n}\right) - f(c)\right) = \lim_{h \to 0^+} \frac{f(x+h) - f(x)}{h}]

rocky lotusBOT
glass kelp
glass kelp
#

and that the limit on the right is definition of the right derivative

ebon thorn
#

Yeah.

glass kelp
#

cool

ebon thorn
#

I am done. I am retiring for the rest of this ass of a class

glass kelp
#

can u think of a function that has a right derivative

#

but doesnt have a derivative there?

#

hint: stay positive!

ebon thorn
#

Positive lol

#

There is nothing positive about this

#

Why can they use |x| but I can't use x?

glass kelp
#

the right derivative exists

#

but doesnt match with the left one

glass kelp
storm birch
ebon thorn
glass kelp
storm birch
#

Alright u seem smart

ebon thorn
glass kelp
#

+1

ebon thorn
#

Yeah, it works for my case as well

#

f(x) = x

glass kelp
#

no

#

derivative exists everywhere for x

gleaming kindle
#

a counterexample requires f'(c) DNE

ebon thorn
#

Same for |x|

glass kelp
#

f'(0) DNE for |x|

#

but f'(0) exists for x

ebon thorn
#

What is the derivative of |x|

wraith heart
ebon thorn
#

There is a point at 0

wraith heart
ebon thorn
#

-1

#

right side is 1

glass kelp
#

so |x| is not differentiable at 0

ebon thorn
#

x is not differentiable at 0

wraith heart
#

,tex .abs def

rocky lotusBOT
#

riemann

wraith heart
#

$\frac{d}{dx} x = 1$

rocky lotusBOT
#

riemann

ebon thorn
#

This didn't prove me wrong

glass kelp
wraith heart
#

yes it does if you know the definition of differentiable

ebon thorn
#

The derivative must exist at each point in the domain

#

It does

glass kelp
#

so it is differentiable

wraith heart
#

x or |x| ?

glass kelp
#

f(x) = x is differentiable

ebon thorn
wraith heart
#

Lol

ebon thorn
wraith heart
glass kelp
#

f(x) = |x| is NOT differentiable at x = 0

wraith heart
wraith heart
glass kelp
ebon thorn
wraith heart
# ebon thorn -1

did you actually do the work to calculate here or did you just guess

ebon thorn
glass kelp
#

[ f'(c) = \lim_{h \to 0} \frac{f(c+h)-f(c)}{h}]

ebon thorn
rocky lotusBOT
gleaming kindle
#

lets chill out

glass kelp
#

ok

wraith heart
ebon thorn
ebon thorn
glass kelp
ebon thorn
#

Your bad at helping

ebon thorn
vale dockBOT
gleaming kindle
#

@ebon thorn dont bite at helpers

glass kelp
hot tide
ebon thorn
gleaming kindle
#

@wraith heart its prob best to step out

glass kelp
#

and a limit doesnt exist if left and right limit arent equal

ebon thorn
#

They can go welcome themselves to another channel

#

Thank you.

#

I never want to see his face in a channel that I occupy again

gleaming kindle
#

i said dont bite

ebon thorn
#

I put the dog down if it bites me first

glass kelp
#

anyhowwwwww

ebon thorn
glass kelp
ebon thorn
#

Take the derivative of |x|

#

Does it exist on 0

glass kelp
#

no

#

it doesnt exist at 0

ebon thorn
#

How so?

halcyon lintel
#

@ebon thorn I agree with you though. @wraith heart is terrible at helping.

glass kelp
#

the left and right limit using the lim defn of derivative arent the same

ebon thorn
#

Does the derivative of f(x) = x exist at 0?

glass kelp
ebon thorn
#

Why does that exist on 0 but not |x|?

wraith heart
#

monkey who is that

ebon thorn
glass kelp
gleaming kindle
#

@halcyon lintel great contribution. take a day off

ebon thorn
#

Is that what you are saying

glass kelp
#

if the left and right limits of smth arent approaching the same thing at the same point

#

the limit of that smth at that point doesnt exist

#

since derivative is defined as a limit of this f(x+h) -f(x)/h

ebon thorn
#

I see.

#

Okay, so the derivative of f'(0) wouldn't exist

#

For |x|

glass kelp
#

yes

ebon thorn
#

Alright

glass kelp
#

can u use f(x) = |x| as the CE for the question

ebon thorn
#

I assume yes because it would give us 1

#

but it doesn't exist at f'(0)

glass kelp
#

can u structure a full argument for me to check plz

glass kelp
ebon thorn
#

Can you structure the entire argument? I don't think I got everything you siad

glass kelp
#

what do u not understand pandathink

ebon thorn
#

Maybe if you laid the entire proof out, I could identify it

glass kelp
#

!noans

vale dockBOT
#

The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.

ebon thorn
#

Well, how tf am I supposed ot know?

#

I can't know unless I see the proof

glass kelp
#

we gave u the ideas

#

for the proof

gleaming kindle
#

we're not obligated to give full answers. it should be smth you can figure out thru guided convo

ebon thorn
#

Well - I will just use the ss because it had it all.

glass kelp
#

alrighty then

ebon thorn
#

.close

vale dockBOT
#
Channel closed

Closed by @ebon thorn

Use .reopen if this was a mistake.

vale dockBOT
#
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grim gazelle
#

can someone give an example on how to solve this?🥲 Its about number systems, our prof made us do self learning, I don’t know what method to use to solve this efficientlycat_cry

cobalt crow
#

like you need to go from decimal number rep to binary

#

no?

#

sorry idk how to do that, let me check youtube and i come back if i learnt it

vale dockBOT
#
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lapis dagger
#

I am struggling with the last part of this question. How do I find the linear combination?

keen trench
#

youre just asked to find like

#

a,b,c such that av1+bv2+cv3 = v5

lapis dagger
#

Yeah, but, how do I do that

keen trench
#

you can setup a system of equatiosn

lapis dagger
#

Sorry I think you're gonna have to spell it out a little more

keen trench
#

so we want to solve like

#

a(1 0 0) + b(-1 1 0) + c(-1 2 1) = (-1 2 1)

#

for the left side to equal the right side

#

wed need that the first components are equal right

lapis dagger
#

Ah ok

keen trench
#

so you would have to have like

#

a - b - c = -1

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then similiarly for the second component

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b + 2c = 2

lapis dagger
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Right

keen trench
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and c = 1

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for the third component

lapis dagger
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ok that makes sense

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Thank you very much

keen trench
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👍

lapis dagger
#

.close

vale dockBOT
#
Channel closed

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Use .reopen if this was a mistake.

vale dockBOT
#
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rough tide
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hey, could someone check if this differentiation is correct? x and y were originally in degree form, and 2 is the multiplier for the entire function.

vale dockBOT
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@rough tide Has your question been resolved?

rough tide
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<@&286206848099549185>

minor spire
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what

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is it given that x/2 is in degrees??

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@rough tide

rough tide
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yes

rough tide
minor spire
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it is correct from what i see

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is this from any book??

rough tide
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it’s my own equation

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wait lemme show u why im doubtful of this

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the setting is in radian

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red being the equation i have, and blue the result of my differentiation by hand

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and green the automaatic differentiated one

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idk y they wld provide different result if it is differentiated correctly

minor spire
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remove the 180/pi from the second graph

rough tide
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okok bet

minor spire
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and lemme do it myself once the differentiation

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one more thing

rough tide
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yea

minor spire
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had you thought first simplifying the eqn and then solving for slope??

rough tide
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wdym

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the original eq?

minor spire
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yes

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try simplifying it once to get f'x

rough tide
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okok

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in radian form or degree form

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bc i hv a reason to keep the results and equations strictly in degrees

minor spire
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why is that??

rough tide
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where i come up w my own research question

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and the question is basically about how FOV in videogames

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which is always in degrees

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so it has to be degrees i feel

minor spire
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okok

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umm

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what about taking 2 to other side and then taking tan both sdies

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leadding to tany/2 = 16/9tanx/2

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try this once

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x is in deg

rough tide
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oh yea

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so

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basically

minor spire
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hmm

rough tide
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the equation was set up like that bc

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i have to make y the subject

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bc y represents horizontal FOV and x represents the vertical FOV

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and in the game i chose u can only shift the vertical FOV

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so the whole equation's purpose is to convert vFOV into hFOV

minor spire
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oh so its a relation between the y and x axis coordinates of players fov

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al;right

rough tide
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yes

minor spire
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lemme do it the hard way then

rough tide
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ooo

rough tide
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its relation into

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how hFOV changes as vFOV changes

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idk if thats what u said

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but yea

minor spire
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but on another note the result will be the same this way too since in the end your just calculating dy/dx

rough tide
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yea thats true

minor spire
rough tide
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oh ok mb

minor spire
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how y changes wrt x

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no no np

rough tide
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yup

minor spire
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right kay lemme try

rough tide
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okok ty