#help-38

1 messages · Page 212 of 1

jolly saffron
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I think you're gonna have to do the same thing here

marsh forum
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got it

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I can then just draw a path that adds a circle around the origin

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and I'm done

jolly saffron
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basically this .(dx, dy), and evaluate the line integral clockwise on the unit circle around the origin

marsh forum
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so it's just 2π

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thanks

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vagrant imp
#

For this Question I am trying to find the equation of the line in the form a+λb, and I have found (the direction ratio for the line) b=-i+2j-k by using the cross product but Im not sure how to find a

jolly saffron
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hmm

dull pilot
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more jee bros

jolly saffron
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i fucking hated this topic given how boring it was

chilly bobcat
vagrant imp
jolly saffron
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man didn't you have some dumb formula for this

vagrant imp
jolly saffron
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with like a determinant

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or something

dull pilot
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not really

vagrant imp
dull pilot
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id like

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assume a random point on one of the lines

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find the normal

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do stuff

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idk

jolly saffron
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yeah the procedure was to use a random point

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snd then you project it to find the smallest distance

ember fern
jolly saffron
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which is the perpendicular

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if I was near a computer I'd use paint but I'm not

vagrant imp
jolly saffron
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yeah I know

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so you assume the point is governed by a parameter t or something

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and the random point that you take

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the projection of that would coincide with t

vagrant imp
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oh so basically like (2t+1)-λ=3u+2
and do that for y and z and solve for u or t

vagrant imp
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spark wagon
#

People, how do I find general solution to this ODE? I got as far as dy/dx = (-2yx^3)/(x^4+y^4) but this doesn't seem to be separable

spark wagon
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and I don't know what substitution to use here

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my notes mention something called "Integration Factor" but I don't know how to apply it here

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if it's applicable to begin with

wraith hinge
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substitute x/y=t

spark wagon
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ok let's see

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oh wow, i am not completely stuck anymore

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i think i'll figure out the rest myself, thx

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wraith hinge
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pliant thistle
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In triangle ABC, (b sin C)(b cos C + c cos B) = 42. Compute the area of the triangle.

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pliant thistle
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zealous sigil
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Hi, I was hoping someone could help me double check my answer for this part c of this question. I think it's correct but I'm not 100% sure to be honest. Thanks!

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@zealous sigil Has your question been resolved?

zealous sigil
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<@&286206848099549185>

zinc raptor
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it's correct

zealous sigil
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If it's okay, would you be able to help me with one or two more?

zinc raptor
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sure

zealous sigil
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This next one is a bit tricky for me

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I have this so far

zinc raptor
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it can be easy to go down the wrong path here

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the key is to think about each of the 50 balls independently

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for starters, what is the expected value of the first number

zealous sigil
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Oh wait sorry do you mean the expected value of the number of times a 1 is observed?

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That would be 1/20 I think

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That's from the previous question

zinc raptor
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i meant the expected value of the number on the ball drawn

zealous sigil
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Oh okay

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To be perfectly honest I'm sure what it would be

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I'm trying to define some variable but I'm not even sure where to start

zinc raptor
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maybe it helps to scale it down first

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suppose you only have two balls, numbered 1 and 2

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and you draw one of them at random

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what is the expected value of the number you get?

zealous sigil
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1.5?

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I think

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Yeah I think its 1.5

zinc raptor
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yeah

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how did you get that

zealous sigil
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Well I found the probability of getting a 1 first which was 1/2

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and the probability of getting a 2 first which was 1/2

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and then (1)(1/2)+(2)(1/2)

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=1.5

zinc raptor
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ok nice

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now you can do the same thing if you have 1000 balls from 1 to 1000

zealous sigil
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But in this one aren't we continuously taking out 50

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In the example you just gave we only choose 1 ball

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and that's it

zinc raptor
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yes

zealous sigil
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So I thought it would be different

zinc raptor
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but if you look at the first ball

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nothing else has been chosen yet

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so it's the same scenario

zealous sigil
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Oh so we are only thinking about the very first one

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That we choose

zinc raptor
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yeah for now

zealous sigil
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Is it 500.5

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I got that by doing this summation in a calculator

zinc raptor
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yes that's correct

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do you know how to compute this sum without a calculator

zealous sigil
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I think there's some formula or something

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Oh wait we could take out the 1/1000 constant term and then use that formula

zinc raptor
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yes

zealous sigil
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This one

zinc raptor
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btw, one way to arrive at the formula is to pair up the numbers

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1 + 1000 = 1001, 2 + 999 = 1001, 3 + 998 = 1001, etc

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but i guess this is not directly relevant to the problem

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anyway, we got that the expected value of the first ball is 500.5

zealous sigil
zinc raptor
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now what about the second ball

zealous sigil
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But we don't know which one was picked on the very first one so I'm kind of confused a bit

zinc raptor
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ok so, the way we calculated it for the first ball is

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we found the probability that the ball is each number

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which is just 1/1000 for any number

zealous sigil
zinc raptor
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so maybe for starters, what is the probability that the second ball is 1?

zealous sigil
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But hold on, if the first ball picked was actually 1 then it's 0

zinc raptor
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yeah

zealous sigil
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I think

zinc raptor
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that's correct

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and the first ball has a 1/1000 chance of being picked, right

zinc raptor
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so how do we combine these to find the probability the first ball is picked on the second turn

zealous sigil
zinc raptor
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no worries

zealous sigil
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First ball picked on the second turn

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I'm not too sure what that means

zinc raptor
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by first ball i meant ball 1

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ok i see the misunderstanding

zealous sigil
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Oh so we want ball 1 to be picked on the second turn

zinc raptor
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we want P(second ball picked = ball #1)

zealous sigil
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Then (999/1000)*(1/999) right

zinc raptor
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yep exactly

zealous sigil
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Oh what the heck it's just 1/1000

zinc raptor
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yeah

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that's very interesting

zealous sigil
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I didn't expect P(first ball is 1) to be equal to P(second ball is 1)

zinc raptor
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what about P(second ball picked = ball #2)?

zealous sigil
zinc raptor
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yeah

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because there's nothing special about ball #1

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the same math works for everything else

zealous sigil
zinc raptor
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so what would be the expected value of the second ball picked

zealous sigil
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By any chance

zinc raptor
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yeah

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because all the probabilities are still 1/1000

zealous sigil
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But how would that make sense from the E(X) formula though

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Let X2=The ball picked on the second turn

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P(X2=1)=P(X2=2)=...=P(X2=1000)=1/1000

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But there aren't 1000 balls to choose from anymore right

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So E(X2)=Sum(X2*P(X2=x2)) or whatever it is

zinc raptor
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however

zealous sigil
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I get how the probability is the same

zinc raptor
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the 999 remaining balls can be any 999 out of the 1000

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so there are still 1000 possibilities

zealous sigil
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But it just doesn't make sense how the expected value is the same

zinc raptor
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maybe, let's go back to the example with only 2 balls

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we have ball #1 and ball #2

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either we pick ball #1 first and ball #2 second, or ball #2 first and ball #1 second

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so the expected value of the second ball picked is 1/2(1+2) = 1.5

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which is the same as the first ball picked

zealous sigil
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Okay yeah that does make sense

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But if you had to do it by defining a variable and then applying the E(X) formula how would you do it?

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Or is it not possible to do it like that

zealous sigil
zinc raptor
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what are you referring to by the E(X) formula

zealous sigil
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The top one

delicate solar
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Oh

zinc raptor
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this is what we're using

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1(1/1000) + 2(1/1000) + ... + 1000(1/1000)

zealous sigil
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But what about E(X2)

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Where X2 is the second ball picked

zinc raptor
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same thing

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because the probabilities are all 1/1000

zealous sigil
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Yup I agree

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But X2 can't take values {1,2,3,4,...,1000} right

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Because one ball has already been picked

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So you can't sum from 1 to 1000 right

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Which is why I'm confused

zinc raptor
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one ball has already been picked

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but

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we don't know which

zealous sigil
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Yup

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I agree with that

zinc raptor
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i guess

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it might be better to think about it

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as starting before any ball has been picked

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we pick 1 ball, throw it away without looking, then pick a second

zealous sigil
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Or maybe I'm missing something here

zinc raptor
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yes

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like, the second ball could be any of the 1000

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there are 1000 possibilities

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here's another way to think about it

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generate a random permutation of balls 1-1000

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and look at the second ball

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(if this is harder to think about don't worry about it but maybe it helps)

zealous sigil
zinc raptor
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this might also help to understand the symmetry

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i.e. why all the probabilities are still 1/1000

zealous sigil
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But what's just really confusing me is the values that X2 can take

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Like I get the thing that you said about throwing the ball away as soon as it's picked

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But I don't know it just feels weird

zinc raptor
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i guess another way to think about it

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instead of drawing from a bag of 999 balls

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actually nvm

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what i was going to say was

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you are drawing from a bag of 1000 "shrodinger's cat" balls

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where each exists with probability 999/1000

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this might just be more confusing because their existence events aren't independent

zealous sigil
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Or something like that

zinc raptor
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i think the permutation phrasing probably makes it most clear

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any ball could end up in position 2 with equal probability

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it doesn't matter what happens in position 1

zealous sigil
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OHHH WAIT

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Because we could have 1 in the second position

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We could have 2

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We could have 3

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Etc. etc. all the way to 1009

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1000*

zinc raptor
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yeah

zealous sigil
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That's genius okay that makes a lot of sense

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Okay that makes complete sense why E(X2)=500.5

zinc raptor
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yay

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so what about the other 48

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X3 through X50

zealous sigil
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I'm guessing they also have an expected value of 500.5 but I'm just going to quickly double check

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Yup they're all 500.5

zinc raptor
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yep

zealous sigil
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So E(S)=E(X1+X2+...+X50)=E(X1)+E(X2)+...+E(X50)=50*500.5=25025?

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Is that maybe how we would do it then?

zinc raptor
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yes exactly

zealous sigil
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Absolutely genius man

zinc raptor
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glad i could help

bright quarry
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🙏🏻

zealous sigil
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I have a feeling that the expected value doesn't change

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Because X1 can take {1,2,3,...,1000}

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P(X1=whatever number between 1 and 1000)=1/1000

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P(X2=same thing)=1/1000

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It's the same thing

zinc raptor
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yep that's right

zealous sigil
zinc raptor
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no problem, you too 🙂

zealous sigil
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rancid gate
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Anyone who can help me understand why this is true, the topic is RSA cryptographics?

zinc raptor
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are you familiar with euler's theorem?

rancid gate
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Yes

zinc raptor
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so what happens if you take m^(ed)

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and then you add or subtract phi(n) from the exponent

rancid gate
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ed = 1 mod n ?

zinc raptor
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i guess i was just explaining why the centered line is true

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are you given that ed = 1 mod n here?

rancid gate
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no this is for an assignment, i need to explain how RSA works

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but i dont understand how to make proof that RSA can be decrypted and output same input

trim lichen
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maybe state euler's thm in full

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so we are on the same page about it

rancid gate
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a^phi(n) is congruent to 1 mod n, given that gcd(a, n) = 1

trim lichen
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ok right

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so you do then have that m is coprime to n, yes?

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therefore m^(phi(n)) ≡ 1 (mod n)

rancid gate
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yes

trim lichen
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therefore you can add or subtract phi(n) to the exponent on m however many times you wish

rancid gate
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yes

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so we can remove it?

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so it says:
m ≡ 1 (mod n)

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?

trim lichen
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no, we get m^(ed) ≡ 1 (mod n)

rancid gate
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how so?

trim lichen
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er

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oh my bad, do we?

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no, i think i got ahead of myself

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i think maybe im missing a bit of context, but can you provide the theorem this is meant to be part of the proof for

rancid gate
rancid gate
trim lichen
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but you do have that ed = 1 mod phi(n), no?

rancid gate
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yes

trim lichen
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well then

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do you understand that since $m^{\varphi(n)} \equiv 1 \pmod{n}$ we can also say that $m^{ed} \equiv m^{ed - \varphi(n)} \pmod{n}$?

solid kilnBOT
rancid gate
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this is cause of inverse elements right?

trim lichen
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i... wouldn't say so explicitly?

rancid gate
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i dont understand this part

trim lichen
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ok maybe it would be easier to illustrate my point with some numerical examples

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let's consider some stuff mod 10

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phi(10) = 4

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since 3^4 ≡ 1 (mod 10), we have that for any natural n, 3^n ≡ 3^(n-4) (mod 10)

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in other words the exponent can be shifted by multiples of 4 (aka phi(10)) for free

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does that make sense to you

rancid gate
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AH

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yes

trim lichen
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yeah so

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in the same way in your example we can shift the exponent on m by multiples of phi(n) for free

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and this can take us from ed all the way down to the remainder of ed mod phi(n), yes?

rancid gate
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trim lichen
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yeah

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and ed mod phi(n) is just 1

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so you get m^1

rancid gate
#

thanks

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.close

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scenic lion
#

Intuitively, I understand that the triple scalar product gives you the volume of the the parallelepiped. I know that each of the three scalar triple product check if the line is to the left of each of the edges when going trough them counterclockwise. What I dont understand is how to know that the line is on the left or on the right. Note that it also determines which normal of the triangle (front face vs back face) the ray is alinged with. So if going through the triangle in counter clockwise directions you expect the ray to be on the left of all three triangle edges. I just dont understand how the math lets you know whether the ray is on the left of an edge or not. I have attached an image showing the ray-triangle intersection visual and some context.
One more though, if you take A X B and A X B > 0 you know A is on the "left" of B, but nothing here is directly using any edge. all the vectors in any scalar triple product consist of two vectrs from the ray origin to the respective vertices of the edge, and the third is the ray origin going towards the ray direction. So I dont understand how this triple scalar product says if the ray is to the left of the edge or not when we arent directly using the edge.

scenic lion
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also to show definition of the triple scalar product here

trim joltBOT
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@scenic lion Has your question been resolved?

trim joltBOT
#

@scenic lion Has your question been resolved?

fleet bear
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Still trying to parse this myself but here are some thoughts I guess

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If we consider
v = [PQ PA PC]
for that particular viewing direction

v = PQ • (PA × PC)
The vector (PA × PC) points into the triangle. I suppose if we think of the plane with normal PA × PC placed against edge AC (AC must in lie in the plane), dotting the normal with PQ would tell us which side point R is on

scenic lion
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youre not suppose to put that here

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im using this channel lol

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please use one of the open ones

gray elm
scenic lion
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its okay!

scenic lion
scenic lion
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idk if that makes sense or not

fleet bear
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It's like the triangle normal:
You have points P, A, and C. There necessarily exists a plane they all lie in. PA and PC will lie that plane too

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PA × PC is normal to the plane

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Reading your message now

scenic lion
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oh wait i think i see what you mean

fleet bear
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Oh btw

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I made a visualisation in demsms 3d

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Desmos

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Which might help

scenic lion
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is it okay if i see it

fleet bear
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Ofc

scenic lion
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dang that looks good

fleet bear
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Thanks

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Unfortunately no labels cuz desmos 3d doesn't support them yet

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The points are defined at the start

scenic lion
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im still trying to understand why you can tell if something is on the left or right of an edge but im going to play around and see if it clicks. either way thanks for doing that and the effort you put into it

fleet bear
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I feel left and right are the wrong way to look it tbh

scenic lion
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whats a better way to look at it? im open to anything tbh

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i just want to understand it better

fleet bear
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Since you're comfortable with planes, you may take it as which side the line PQ enters/leaves the edge-plane

fleet bear
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Or even as whether the vector PQ has a positive component in the direction of normal (this is for the CCW case)

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I think the viz should help anyway

scenic lion
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i understand it from the first visual now thank you, going to look at this one too now

scenic lion
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.close

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lavish cosmos
#

Working through textbook questions and there are no solutions for this question

I found this proof online but the last part doesn’t make sense to me

If someone could explain or propose a different proof that would help

half marsh
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goodnotes

next vessel
#

ight

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@lavish cosmos Has your question been resolved?

lavish cosmos
#

<@&286206848099549185>

fallow bane
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I think it looks okay

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Are you meant to write your proof in this list format or is a worded proof sufficient

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If the former is true you need to add the axiomatic logic rules at the end of each step to justify what you did

lavish cosmos
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its meant to be a semiformal proof

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mainly words with justifications for each line

I Understand that Y is an element of both but why is it neccessarily true that f(D^E) a subset of f(D) ^ F(E)

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@lavish cosmos Has your question been resolved?

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@lavish cosmos Has your question been resolved?

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wraith hinge
#

so i have trouble trying to simplify this

solid kilnBOT
simple panther
#

I think this is as far we can go

wraith hinge
#

uhhhhhhhhhh

simple panther
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Or did u mean something else?

wraith hinge
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no

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im

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bad

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at

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this

wraith hinge
#

the factorisation is a bit confusing 😭

solid kilnBOT
wraith hinge
#

idek how

solid kilnBOT
wraith hinge
#

im gonna cry

solid kilnBOT
simple panther
wraith hinge
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oh

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i am slowly

simple panther
wraith hinge
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starting to envision this

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so from 16xx and 2x

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uhh

simple panther
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yes

wraith hinge
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2x

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take out 2x

simple panther
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ye

wraith hinge
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idk

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oh

simple panther
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from that, we can take 2x common out

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and from the rest, we can take (1-4x)³ common out

wraith hinge
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2x(8x^(1-4x)^3)+(1-4x)^4

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idk

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or do i need one extra bracket

simple panther
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yes

wraith hinge
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2x((8x^(1-4x)^3)+(1-4x)^4)

#

like this?

simple panther
#

yes

#

you're missing the 2 next to x^

#

it's x^2

wraith hinge
#

wait

simple panther
wraith hinge
#

no wonder why it looked confusing

#

okay

#

yayyyyyy

#

thank you

#

i lvoe you

simple panther
#

and in the remaining part of the terms, there is (1-4x)³ common, that can also be taken out

wraith hinge
#

is that actually the simplest form

simple panther
#

take it out

wraith hinge
#

wait

simple panther
wraith hinge
#

let me write it first

wraith hinge
simple panther
#

oh, yeah

#

it's just x

#

8x

wraith hinge
#

should it look like this

#

also excuse my funny shape of x

simple panther
wraith hinge
#

okay now

#

how do we

#

take out

#

1-4x

simple panther
#

as you can see, there is (1-4x)³ common in the 2 terms

#

the inside part can be written as -8x * (1-4x)³ + (1-4x) * (1-4x)³

wraith hinge
#

hwat

#

oh

simple panther
wraith hinge
#

i get what u maent

#

yes, process

#

I mEAN

#

PROCEED

#

😭

simple panther
#

then, we can take the (1-4x)³ common out and we get

#

(1-4x)³ * (-8x + (1-4x))

wraith hinge
#

ok this is where im stuck

simple panther
#

so, it will be 2x(1-4x)³(-8x + (1-4x))

#

Simplifying it gives 2x(1-4x)³(1-12x)

wraith hinge
#

im tryinh to udnerstad

simple panther
#

??

wraith hinge
#

oh

#

this is what i did

simple panther
#

Yes

#

If that heps you understand it, that be it

wraith hinge
#

yY

#

yayayayay

#

thanksks yuou so much

#

hearts 4 u

#

.close

trim joltBOT
#
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wraith hinge
#

how do i integrate 2/(2x-a)

trim joltBOT
wraith hinge
#

dont i take the 2 to the left of the integral

hybrid vine
#

Sure

wraith hinge
#

then divide it by the derivative

#

so ln (2x-a)?

hybrid vine
#

Derivative of?

wraith hinge
#

2x-a

hybrid vine
#

Yup

wraith hinge
hybrid vine
#

Yes

#

ln(2x -a) + C

wraith hinge
#

oh

#

thanks

#

.close

trim joltBOT
#
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obsidian zealot
#

!status

trim joltBOT
#
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
jolly saffron
#

if the radicals give you trouble sub n = x^60

obsidian zealot
#

perhaps some roots should turn into fractional powers

#

orrrrrrrrrr that

jolly saffron
#

yeah i think that's right

#

,w limit as n goes to infinity (5n^(4/5) - 2n^(2/3))/(2n^(3/4) + 5n)

trim joltBOT
#
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late rivet
trim joltBOT
late rivet
#

this is correct or no

#

granted i can simplify the 54/16

trim lichen
#

looks vaguely correct but i feel like it could be less complicated to begin with.

late rivet
#

how

#

vaguely opencry

#

i just put it in like that as i was going by the terms

#

i got it correct

#

but how did they simplify it to this

#

v

obsidian zealot
#

16=4^2

dapper swift
# late rivet

yeah the trick is just $\frac{9/4}{1 - x^6 / 4}$ so $\sum_{n = 0}^{\infty} \frac{9}{4} (x^6 / 4)^n$

solid kilnBOT
obsidian zealot
#

4^(n-1+2)=4^(n+1

late rivet
#

okay i see

#

thanks

#

.close

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#
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late rivet
#

.reopen

trim joltBOT
#

late rivet
#

what did i do wrong

surreal bone
#

can you show your solution , please ?

late rivet
#

my solution is the bottom

#

with th esunm

#

sum

surreal bone
#

well you need to solve it step by step

late rivet
late rivet
#

and it is wrong

#

idk what i did wrong

obsidian zealot
#

!showwork

trim joltBOT
#

Show your work, and if possible, explain where you are stuck.

obsidian zealot
#

not “stuck” but like

late rivet
#

100% my work will not help but ill show it

#

here

surreal bone
#

did you use this ?

late rivet
#

yeah

surreal bone
#

you need to take care when the sum starts from 0 or from 1

late rivet
#

meaning what

#

it starts at 1

surreal bone
late rivet
#

what do i do

surreal bone
#

you need to take care of the bounds of the sum

late rivet
#

how

surreal bone
late rivet
#

so for every n i have

#

i do -1?

surreal bone
#

as you see

#

then put t = x^9 /2

#

multiply it by 3/2

#

then find f'(t)

late rivet
#

would this be it then

late rivet
surreal bone
late rivet
#

😔

#

okay

#

no

#

that wasnt correct

#

how did they get this

#

<@&286206848099549185>

surreal bone
late rivet
obsidian zealot
#

they used n=0 lower bounds probably

late rivet
#

in their answer

obsidian zealot
#

I’m just saying the answer is correct if you use n=0

surreal bone
wraith hinge
#

If I followed the standard geometric series approach, This is Definitely a bit different

surreal bone
trim joltBOT
#

@late rivet Has your question been resolved?

wraith hinge
#

My solution

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wraith hinge
trim joltBOT
late rivet
#

.repoen

wraith hinge
#

what is happening here

late rivet
#

oh

#

oopsies

wraith hinge
#

sorry

late rivet
#

nah its all good

late rivet
wraith hinge
dull pilot
#

integration

wraith hinge
#

and why didnt we add C to the left side

wraith hinge
#

can i swear?

late rivet
#

also

wraith hinge
late rivet
#

if you added the C to the left side as well they would just cancel out

dull pilot
late rivet
wraith hinge
late rivet
#

bye bye

wraith hinge
#

anyways

late rivet
#

they did u sub

wraith hinge
#

for the x/1+x^2

late rivet
#

u = 1+x^2, du = 2xdx

wraith hinge
#

ohhh there is a rule for it

late rivet
#

du/2 = xdx

late rivet
wraith hinge
#

nvm no rules

#

only if the numerator was 1 i couldve done sometrhing

late rivet
#

wdym

#

like a trig inte??

wraith hinge
#

this rule

late rivet
#

do you understand how they got 1/2 ln|1+x^2|

late rivet
wraith hinge
#

no

late rivet
#

they used u-substitution

late rivet
wraith hinge
#

hold on

#

oh let me try on a piece of paper

late rivet
#

okie

wraith hinge
#

u = 1+x^2

late rivet
#

yes

wraith hinge
#

and i got du = 2xdx

#

now what

#

oh make dx subject

late rivet
#

yes

wraith hinge
#

dx = du/2x

late rivet
#

no

#

not all the way

#

you have xdx

wraith hinge
#

what

#

ohhh

#

so du/2 = xdx

late rivet
#

yes

#

thats where the 1/2 comes from

wraith hinge
#

now i have (du/2) / (u)

late rivet
#

you can pull the 1/2 out

wraith hinge
#

alright

late rivet
#

so 1/2int(1/u)

wraith hinge
#

where did the 1 come from

late rivet
#

where ?

wraith hinge
#

1/u

#

i have du/u

late rivet
#

sorry

#

thats just how i do it

#

i mean
1/2 int(1/u)du

#

du/u works to

wraith hinge
#

ohhh

late rivet
#

mb

wraith hinge
#

alright thanks

late rivet
#

no problem

wraith hinge
#

.close

trim joltBOT
#
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late rivet
#

well i see it

#

.open

#

didnt know that doesnt work

#

anyway

trim joltBOT
#
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late rivet
#

@surreal bone

trim joltBOT
late rivet
#

^

dull pilot
#

huh

#

what

late rivet
#

the stuff above

surreal bone
late rivet
#

i couldnt reopen the channel in time

late rivet
dull pilot
#

...you used .open lol

#

it's .reopen

late rivet
#

no someone took the channel before

dull pilot
#

anyway if you have a guy ill leave you to it

late rivet
#

i did .reopen

#

also the the is n=1

trim joltBOT
#

@late rivet Has your question been resolved?

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proper ferry
trim joltBOT
proper ferry
#

Where does the pi come from when the y do fourier ttansform

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#

@proper ferry Has your question been resolved?

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next vapor
#

The function f(x) = kx + m is given for x ∈ (0,1) and 0 otherwise.

a) What conditions must k and m satisfy for this function to be a probability density function?
Let X be a random variable with density f(x) where now m = -1.

b) Find P(< x <).
c) Compute E(X) and D(-2X).
d) Let Y = 3X - 2. Find the density of the random variable Y.

trim joltBOT
next vapor
#

2

#

i want someone to go throw together

#

<@&286206848099549185>

trim joltBOT
#

@next vapor Has your question been resolved?

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thin vine
trim joltBOT
thin vine
#

can someone please help me with this problem

#

so im pretty sure youre supposed to use half angle formula for tan

#

oh wait

gusty bone
#

yeah just sub and solve the cubic or whatever for cos(x)

trim musk
trim joltBOT
#

@thin vine Has your question been resolved?

thin vine
#

.close

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chilly sparrow
#

Two cars start simultaneously from two reference points A and B at a distance of 500 m, heading towards each other. Car A maintains a constant acceleration of 2.0 m/s2 until it reaches a speed of 20 m/s, continuing in uniform motion (constant speed). Car B always maintains a constant acceleration of 1.0 m/s2.
A. How long after the start do the cars meet?
B. How far from reference point A does the meeting take place?

chilly sparrow
#

I haven't been able to solve this problem 😦

supple copper
#

what have you tried

chilly sparrow
#

It's a bonus for mechanical physics, but I really didn't understand the topic.

supple copper
#

do you understand what the question is asking?

chilly sparrow
#

I know he asks about mechanical physics and something about the MRU

supple copper
#

do you know calculus?

chilly sparrow
#

so so

supple copper
#

can you write down the position of the 2 cars x(t) and y(t)?

ornate bobcat
#

theres basic speed formulae u learn in elementary phy but rest is regular algebra

trim joltBOT
#

@chilly sparrow Has your question been resolved?

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old glen
#

can you explain in second example its 31 / 33 but it could have been with 26 / 215

old glen
#

can i still do it like 3/6 as 1/2 and do not do first step like he has done what is better?

kindred jungle
#

"can you explain in second example its 3*1/3*3 but it could have been with 2*6/2*15"

#

wdym?

old glen
old glen
kindred jungle
kindred jungle
old glen
#

can also do with 2

kindred jungle
#

the 9/15, or the 12/30?

old glen
kindred jungle
#

thats okay

old glen
kindred jungle
#

yes of course, but youll have to simplify it more

#

try doing it with 2

#

see what you get

old glen
kindred jungle
#

youll see

#

just try doing it with 2

#

see what you get

old glen
#

12/30 = 2 * 6 / 2 * 15

#

cancel out 2s and 6/15 = 3/5

kindred jungle
#

6/15 is not 3/5

#

you're very close tho

old glen
#

2/5

kindred jungle
#

yes

#

6/15 is 2/5

old glen
#

moonful you think i can improve my math

kindred jungle
#

you can do it with 2, yes, but itll eventually simplify to 2/5 anyway

kindred jungle
old glen
kindred jungle
#

yes

#

as long as you get a fully simplified answer in the end

old glen
#

but if i was good at math i could do it like he has done it

kindred jungle
#

in general, though, to do it the fastest, you need to look for the largest number you can cancel

old glen
#

i liked this way of doing

kindred jungle
#

which way?

old glen
#

so like i dont have to cancel 3s

#

like directly

kindred jungle
#

yes thats okay

#

nothign wrong with that

old glen
#

is this what i was taught at school

kindred jungle
#

what he's doing is just showing how it works

#

if you can do it directly you're doing great

kindred jungle
old glen
#

oh

#

thanks for a lot of the help @kindred jungle

kindred jungle
#

no probelm

old glen
#

.close

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#
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trim joltBOT
#
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cyan forum
trim joltBOT
cyan forum
#

How can i find a y vector that is equal to: y = a + c

pliant gale
cyan forum
#

hear me out

cyan forum
#

let’s name that point O right

#

i can’t prove that BO = DC to be able to do anything

#

the only hint the exercise gives is that ED // AB, DC//FA and FE//BC

deep prairie
#

Would it be possible if you sent the original question?

cyan forum
#

yeah hold on

deep prairie
#

Thank you!

pliant gale
cyan forum
#

here

cyan forum
#

why would BO = -DC

#

i get that the vectors have different directions

#

but for now i need to prove that |BO| = |DC|

#

so i can then say that BO = c

#

i’m trying to somehow prove that DCBO is a rectangle

#

it can even work out if it’s a parallelogram

#

but ive honestly tried everything

deep prairie
#

It’s so sad that it doesn’t say the diagram is drawn accurately

#

Have you tried using angles to prove it?

deep prairie
#

🥲

cyan forum
#

i’m trying to utilise that those sides are parallel to play with angles but nothing seems to be working out

cyan forum
#

nope

deep prairie
#

I wish I could be more use but proving stuff with vectors is like a mind game to me

#

Sorry

pliant gale
#

Do they told u how works Vectors' coordonate

#

Or vectors' distance ?

cyan forum
#

hm?

pliant gale
cyan forum
#

well it’d be too much if i used cords

pliant gale
#

Without it, I don't rly know how to prove it

cyan forum
#

welp

trim joltBOT
#

@cyan forum Has your question been resolved?

cyan forum
#

<@&286206848099549185>

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#

@cyan forum Has your question been resolved?

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gusty bone
#

Let $e(x)$ be an even function, and let $o(x)$ be an odd function, such that
[e(x) + o(x) = \frac{6}{x + 2} + x^2 + 2^x]for all real numbers $x \neq -2.$ Find $o(1).$

solid kilnBOT
#

Dork9399

gusty bone
#

All i know is that an even function implies that f(x) = f(-x) and odd implies -f(x) = f(-x)

jolly saffron
#

did you also know that any function can be broken down into odd and even components like that

#

atleast continuous ones can

jolly saffron
#

I suppose that's simpler

trim lichen
#

(there is a meaningful answer and a cop-out answer to this. i want the former!)

gusty bone
#

i think i got the cop out answer 😭

trim lichen
#

no

jolly saffron
#

the cop out answer would be 1

trim lichen
#

the cop-out would have been to say e(1)

#

yes so

#

e(1) = e(-1)

#

can you do the same thing for o, but obviously keeping in mind that it's odd

gusty bone
#

o(1) = -o(-1)

gusty bone
trim lichen
#

ok

#

now take this: $$e(x) + o(x) = \frac{6}{x + 2} + x^2 + 2^x$$ and put $x=1$.

solid kilnBOT
trim lichen
#

don't simplify e(1) + o(1) yet. keep it as it is.

gusty bone
#

e(1) + o(1) = 2 + 1 + 2 = 5

trim lichen
#

good

#

now put x=-1 instead.

gusty bone
#

e(-1) + o(-1) = 6 + 1 + 1/2 = 15/2

#

oh wait

#

oh lol

#

what a solution

#

x + y = 5, x - y = 15/2

trim lichen
#

yes

#

and your goal is y

gusty bone
#

so o(1) = -5/4

#

oh i thought it was so much more complex

trim lichen
#

you sure you didnt find e(1) on accident

gusty bone
#

whoop

#

i thought i had to separate the function into odd and even components 😭

#

this is so much simpler

#

.close

trim joltBOT
#
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lunar stirrup
trim joltBOT
lunar stirrup
#

i put a=b=c=0

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then got val of determinant as x^3

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so it should be divisible by all right

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but answer key is showing only 1 and 2

frozen plover
#

you might lose some information with that sub

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put everything to be 1 instead

lunar stirrup
#

oh

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that kinda makes my life harder

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but okay ill try that

frozen plover
#

not like you're meant to be doing it this way anyways lol

cunning cliff
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why that sub

frozen plover
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maybe you could let one parameter be 0 actually

cunning cliff
#

that sub tells you that you can't rule out x, x^2, x^3

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if you got the determinant to be 1 for example, with that sub

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then you know the answer is "none of these"

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but since you got x^3, it gives you nothing to go on

frozen plover
#

scamming is an art

lunar stirrup
frozen plover
#

maybe with a different sub you get x^3 + x

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so it's no longer divisible by x^3

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with your sub you know at most it's divisible by x^3, x^2, and x

lunar stirrup
frozen plover
#

not exactly y

lunar stirrup
#

otherwise the answer would be subjective

frozen plover
#

but that doesn't mean that it would hold for your case

cunning cliff
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let me give an example

frozen plover
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if the answer is x and x^2, x^3 is still divisible by them

cunning cliff
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"Is 5x divisible by 3"

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when someone asks this

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it is implicitly for all integers x

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clearly if we choose x = 0 it is divisible by 3

lunar stirrup
#

huh

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so what would u suggest i do to solve it

cunning cliff
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compute the determinant normally

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algebraically using whichever method you usually do

lunar stirrup
cunning cliff
#

stop being lazy

lunar stirrup
#

,w det{{a^2 + x,ab,ac},{ab,b^2+x,bc},{ac,bc,c^2+x}}

cunning cliff
#

sigh

lunar stirrup
cunning cliff
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it shouldnt take you 2 minutes to compute the determinant with some practice

lunar stirrup
#

fair

frozen plover
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and yeah this time letting one of the parameters be 0 and the other 2 be 1 works

lunar stirrup
#

oh ok yeah

cunning cliff
#

again, that doesn't give you certainty

frozen plover
#

have faith

cunning cliff
#

You only have certainty after a substitution if it turns out its not divisible by x

lunar stirrup
#

,w det{{a,-1,0},{ax,a,-1},{ax^2,ax,a}}

lunar stirrup
#

@cunning cliff @frozen plover ty guys i got this one right (didnt put a =0 )

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i think this is one specific type of problem where u are not allowed to put = 0

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cause it worked for most of the others

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,w det{{1,3,1},{3,4,1},{2,3,1}}

lunar stirrup
#

,w det{{1,9,1},{9,16,1},{4,9,1}}

lunar stirrup
#

.close

trim joltBOT
#
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Closed by @lunar stirrup

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wraith hinge
trim joltBOT
wraith hinge
#

<@&286206848099549185>

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I NEED HELP

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😭

umbral hazel
#

!15m

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wraith hinge
#

ohh

umbral hazel
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What can you tell me about the sequence?

wraith hinge
#

uhhhhhh

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for the first one

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6n+9

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but

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it says 3n

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so shouldn't it be

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18n squared +9

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18n²+9

trim joltBOT
#

@wraith hinge Has your question been resolved?

wraith hinge
#

<@&286206848099549185>

umbral hazel
#

My bad

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I’m at an event for my Younger Sister’s school

umbral hazel
#

So 6(3n) + 7

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@wraith hinge Still here?

trim joltBOT
#

@wraith hinge Has your question been resolved?

trim joltBOT
#
Channel closed

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#
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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>.
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vocal cobalt
#

how do I solve part d? I'm kinda stuck

trim joltBOT
burnt mulch
solid kilnBOT
#

Civil Service Pigeon

vocal cobalt
burnt mulch
#

That is what I said 😕

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b/c atm, you only have info about the arc length of f, and hence about the integral of sqrt(1+(f'(x))^2)