#help-10

1 messages · Page 299 of 1

inland matrix
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Coz they can be in any interval in general

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Oh

ember frost
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ah youre damn right

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i think i can take it from here

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many thanks

brazen gorge
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np

ember frost
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.close

obtuse pebbleBOT
#
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sick badge
#

Given an M/M/1 queue with arrival rate lambda and service rate mu. If a customer arrives at a random time and the queue is empty, and we don't know if the server is busy, how do we calculate the probability that the server is busy?

timid silo
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seems like a poisson process

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and they want you to use an Erlang distribution or something thonk

sick badge
#

Suppose arrival rate is 1 and service rate is 3 for system stability how would I calculate the probability the server is busy when the queue is empty?

obtuse pebbleBOT
#

@sick badge Has your question been resolved?

obtuse pebbleBOT
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shy shoal
#

was wondering on how to do this type of question for polynomial functions?

jovial portal
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You can do some equations for a general polynomial of order 5 and slove recursivly

high lily
#

identify the zeros,
respective factors from factor theorem, then their power based on the shape of the curve around that zero
introduce scaling factor, determine that from the given g(0) = -2

shy shoal
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so my original equation is p(x) = (x+1) (x-1)^2 (x-3)^2

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cause those tare the zeroes but idk

jovial portal
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Looks good now input the g(0) = ... and you get the scaling factor

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actually i thing it should be $p(x)= a \cdot (x-1) (x+1)^2(x+3)^2$

warm shaleBOT
high lily
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you're not applying factor theorem correctly

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if $k$ is a zero, $(x\red{-}k)$ is a factor

warm shaleBOT
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ℝαμΩℕωⅤ

shy shoal
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so my original equation is not complete yet?

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im not sure on what to do after that

high lily
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its outright wrong

shy shoal
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oh crap

high lily
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because you didn't aply factor theorem properly

shy shoal
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im not so sure what to do

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i know my zeroes are

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1 -1 and -3

high lily
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do you know what factor theorem states?

shy shoal
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not really

high lily
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i made an extremely brief summary above

shy shoal
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ok so if i take example of 1 as a zero

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then x-1 is a factor

high lily
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yes

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and from the graph what's the multiplicity of that zero?

shy shoal
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1

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since it passes through

high lily
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yeh, now move onto the next zero

shy shoal
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so -1 as a zero

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x+1 is a factor

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and since it bounces the multiplicity should be 2

high lily
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yes

shy shoal
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so x+1^2

high lily
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()

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(x+1)^2

shy shoal
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oh yeah mb

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then

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(x+3)^2

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ohhh i see now

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so p(x) = (x-1) (x+1)^2 (x+3)^2

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?

high lily
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you'd want a scaling factor

shy shoal
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what's that?

high lily
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p(x) = a(x-1) (x+1)^2 (x+3)^2

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where a is to be determined

shy shoal
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oh i see

high lily
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what you currently have is a specific polynomial with those zeroes that doesn't necessarily satisfy the other condition

shy shoal
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so we find a

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but the y intercept isnt given

high lily
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you're given g(0) = -2
don't know why they used different names here

shy shoal
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oh but it said g(0) = -2

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so do we replace p(x) with -2?

shy shoal
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the reviewer

high lily
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you replace x with 0 and p(x) with -2
in the same step

shy shoal
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ohhh i see

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so

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0 = a(-2 - 1) (-2+1)^2 (-2+3)^2

high lily
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no

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you replaced things the other way

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you replaced x with -2 and p(x) with 0

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which isn't what you're supposed to do

shy shoal
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oh so

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-2 = (0-1) (0+1)^2 (0+3)^2

high lily
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yes

shy shoal
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oh yeah my bad since p(x) is 0

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i get it

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i got 2/9 as the a

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so p(x) = 2/9 (x-1) (x+1)^2 (x+3)^2

high lily
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yes

shy shoal
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thats our complete equation?

high lily
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yeh

shy shoal
#

thanks a lot!

obtuse pebbleBOT
#

@shy shoal Has your question been resolved?

obtuse pebbleBOT
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blissful bane
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How do I find the integrating factor for a differential equation of the form M dx + N dy =0 to make it exact ?

inland matrix
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Are M and N constants or functions?

blissful bane
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functions of x and y

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M(x,y) and N(x,y)

inland matrix
#

Oh

obtuse pebbleBOT
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@blissful bane Has your question been resolved?

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@blissful bane Has your question been resolved?

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sullen sparrow
#

hi! i am studying vectorial subspaces and i dont understand why P3(x) is contained in P(x). isnt P3(x) greater than P(x)?

pseudo swift
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alright

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so what do you think P(x) and P3(x) is then ?

fallow island
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by contained you mean it being a subspace?

sullen sparrow
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polynomials

sullen sparrow
pseudo swift
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that's not very specific though

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that doesn't tell me what the difference between P(x) and P3(x) is

sullen sparrow
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like

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isnt p2(x) a polynomial like c + x + x^2 and p3(x) like c + x + x^2 + x^3?

pseudo swift
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ok ok

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well p2(x) has all polynomials of degree less than or equal to 2

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p3(x) has all polynomials of degree less than or equal to 3

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etc...

sullen sparrow
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yeah yeah

pseudo swift
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otherwise they're not vector spaces at all

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and P(x) contains all polynomials

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whatever their degree

sullen sparrow
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hmm

pseudo swift
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so why would P2(x) not be contained in P(x) in that case

sullen sparrow
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so, p(x) is like R for real numbers?

pseudo swift
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not sure what you're saying here

sullen sparrow
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uhm

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im still not sure what p(x)

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like

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its contains all polynomials, but like

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its a universe of polynomials then??

pseudo swift
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I guess

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but like P3(x) would also be a 'universe' of polynomials if I understood you correctly, there are also polynomials inside of it

sullen sparrow
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yes

pseudo swift
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so maybe you should clarify what you mean by 'universe of polynomials'

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okok

sullen sparrow
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yeah like

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the biggest one

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i got it

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idk how to verbalize my thoughts, but i got it

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tysm

pseudo swift
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but yeah P(x) is the biggest one indeed

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you're welcome

sullen sparrow
#

.close

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placid rose
#

Can you help me understand why this is wrong?

placid rose
#

I was testing it and it says I’m wrong

obtuse pebbleBOT
#

@placid rose Has your question been resolved?

placid rose
#

no

obtuse pebbleBOT
#

@placid rose Has your question been resolved?

placid rose
#

No

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Y’all don’t help

placid rose
#

Oh wait

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Bro

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I know I messed up but

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It’s okay

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I can close this

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And nobody will remember

#

It will fade away into obscurity

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And be gone 10000 messages away

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.close

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hoary idol
#

right isosceles triangle there is a circle on it that circle toches 1 side and its center is at the hypotnus and the circle also toches the shatrp corner i need to find the radius

obtuse pebbleBOT
#

Please don't occupy multiple help channels.

hoary idol
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cinder ridge
obtuse pebbleBOT
cinder ridge
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look at the cylinders part of my teacher's work

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the formula for the cylinder is 2pi * r * h * delta x

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i can kind of see why he didn't include delta x in the integral function

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but in this case should we have included it or not?

obtuse pebbleBOT
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@cinder ridge Has your question been resolved?

cinder ridge
#

he used the formula again and he made delta x magicaly disappear

obtuse pebbleBOT
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@cinder ridge Has your question been resolved?

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surreal mountain
obtuse pebbleBOT
surreal mountain
#

How do i approach this?

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(The anser should be written as x + iy)

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Im thinking de moivres

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But its my first time using it

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So im not sure what to do

brazen gorge
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convert to either cis form or polar form

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each bracket

surreal mountain
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Ok

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That will take some time

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Working on it

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I want to rewrite the 25 as something smaller

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But i have messed it up before

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What is a good method for doing it?

brazen gorge
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cos(25pi) = cos(pi)

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same with sin

surreal mountain
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But how would i write it out?

brazen gorge
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not sure tbh

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but do you understand why that is?

surreal mountain
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I have a small clue

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Both functions are periodical

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By 2Pi

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But how do i know its not = cos(0)?

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Do i think of the closedt number possible to 25 (24) and the diffirence will be the answer?

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25Pi - 24Pi = 1Pi

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So cos(Pi)?

surreal mountain
brazen gorge
#

aka reduce mod 2pi

obtuse pebbleBOT
#

@surreal mountain Has your question been resolved?

surreal mountain
#

.close

obtuse pebbleBOT
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glacial widget
#

Pleaseeee help with this question.
Its intergration by parts. ill send the question and then my work. I cannot understand for the life of me whats going wrong lol

glacial widget
#

let me send the photos from my phone

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so i did the box where i chose
e^-x as my intergration.
and 3x-4 as my dx

so that should be

d = 3
intergration = -e^-x

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so using intergration by parts it should be

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= (3x-4)(e^-x) - INTERGRATION OF: (3)(-e^-x)

multiplying inside the intergration before to simplify

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its then

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= (3x-4)(e^-x) - INTERGRATION OF: (-3e^-x)

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then intergrating it its

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should be

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(3x-4)(e^-x)-(3e^-x)+C

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but thats wrong. im so confused lol

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any help is appreciated! pls ping me ❤️ thanks

obtuse pebbleBOT
#

@glacial widget Has your question been resolved?

alpine oar
#

@glacial widget can you try multiple answers?

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does it have to be simplified a certain way or is any correct answer acceptable?

glacial widget
#

yeah

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i can try any answers

alpine oar
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well okay for starters do you know the tabular method?

glacial widget
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no

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i was only taught this square thing

alpine oar
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okay so you need to do integration by parts, you divide the the integral into two parts, the first part will be the bracket, and the second part will be the exponential function which is the (e^-x)

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you select one to differentiate and one to integrate

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ill show you on paper hold on

glacial widget
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heres another example

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i just dont understand wtf im doing wrong

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like this is literlaly right

alpine oar
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okay hold on let me try it

glacial widget
#

i just dont really undesrtand why youre suppsoed to multiply the stuff inside the intergration before intergrating

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ok i solved the firstt one

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i need the 2nd one now

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thats hte one im really not understanindg

alpine oar
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hey sorry im late

glacial widget
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its ok!!

alpine oar
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can you check the last answer and see if it will work, or does it need to be simplified

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if it does, then I think I can explain it to you

glacial widget
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lemme put it in

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its gonna take me a bit to type with parenthese one sec lol

alpine oar
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alr tyt

glacial widget
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oops

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wait

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wrong e^x

alpine oar
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its

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e^4x

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also put the parentheses around the whole thing except the C

glacial widget
#

my prof is gonna be sooo confused

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LOL

alpine oar
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uhh

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the e^4x is supposed to be a common factor of the 3 fractions, is it written that way?

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its not in the preview is it a bug

glacial widget
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what

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what does that mean

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😭

alpine oar
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you have 3 fractions right

glacial widget
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yes

alpine oar
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they're all supposed to be * e^4x

glacial widget
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oh

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yes

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i added anotehr parnthesis

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in that case its right

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my bad

alpine oar
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hmm

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I wonder what the problem is idk

glacial widget
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but i have no idea how u got to that lol

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bc the way im taught is this stupid square theory

alpine oar
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wait

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is it correct?

glacial widget
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uya

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ya

alpine oar
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OH OK NOW I CAN EXPLAIN

glacial widget
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please dfo

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Ll

alpine oar
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okokok do you learn better by visuals

glacial widget
#

lol

alpine oar
#

should I open paint

glacial widget
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the way i was taught is thi weird

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square thign

alpine oar
#

no no I mean like you want me to type it or open paint and explain on it

glacial widget
#

forgive the bad handwriting but

alpine oar
#

its fine lol

glacial widget
#

you differentiate the algebric term and intergrate the e

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and then

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its

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a diagnol multiplication

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and then - intergration of the multiplied bottom two

alpine oar
#

yeah but this complicates stuff

glacial widget
#

😭

alpine oar
#

hold on

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ill write it down

glacial widget
#

I appreciate your help but I have to show my work in the stupid box way. ill just go to the Ta's or something unfortuantely

alpine oar
#

this method is similar to it

glacial widget
#

i just do not understand why i am getting it wrong

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even using the box way

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my work is right

alpine oar
glacial widget
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uhh

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what

alpine oar
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when you start out

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you do the box thing

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its the product of the diagonal

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and a new integral

glacial widget
#

yea

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yes

alpine oar
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okay so the new integration

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is a new box

glacial widget
#

yes

alpine oar
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did you do the new box

glacial widget
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i dont

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do new boxes

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i just

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writ in the formula

alpine oar
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okay because the new box yeilds another box which is the last one in this case

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but instead of boxes

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you can write a table

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it's better

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let me show you

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okay start by typing it like this

glacial widget
#

😭 i have no idea what im looking at

alpine oar
#

up top is the integration question

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you draw a line splitting the page

glacial widget
#

heres an example of one i just got right

alpine oar
#

column on the left (D) stands for differentiate, column on the right (I) stands for integrate

glacial widget
#

(all by myself yay go me)

alpine oar
#

yay go you actually

glacial widget
#

LOL

alpine oar
glacial widget
#

I dont understand waht that one is trityng to say though

glacial widget
#

like i dont get the + - thing

alpine oar
#

yeah thats part of it

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when you write the table

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you alternate between + and -

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let me take you step by step hold on

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you split the page

glacial widget
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which is the box thing basically

alpine oar
#

yes

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you add the + and -

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start with the +

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and alternate

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you dont usually use them all, but add a bunch just to make sure

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thats step two

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got it?

glacial widget
#

ys

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yes

alpine oar
#

okay now you have 2 parts of the integration

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which should we differentiate and which should we integrate

glacial widget
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well

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LAE

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Dx the x^2-7

alpine oar
#

alright

glacial widget
#

and intergrate e^4x

alpine oar
#

write it down and show me

glacial widget
#

where do i put them

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on the

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  • thing
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like just the next line

alpine oar
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on the first +

glacial widget
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OH

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WAIT

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CRAP

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its

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that rule is so stupid i hate it sm lol

alpine oar
#

okay now when you have a function that can reduce to 0 by differentiation

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you keep going till you reach the 0

glacial widget
#

whaaat

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😭

alpine oar
#

you have x^2 - 7 right

glacial widget
#

yes

alpine oar
#

when you keep differentiating that

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whats the last product you're gonna get?

glacial widget
#

ohhh

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2

alpine oar
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and then?

glacial widget
#

0

alpine oar
#

yes

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you reach the 0

glacial widget
#

write that on the next lines?

alpine oar
#

that's your first stop

glacial widget
#
  • 0
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OMG STOP DISCORD

alpine oar
#

you stop when you reach 0

glacial widget
#

minus -

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0

alpine oar
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you have 2x now

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its gonna be 2

glacial widget
#

omg but intergrating is gonna take forever

alpine oar
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then 0

glacial widget
#

for the

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next lines

alpine oar
#

no not that long

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you just divide by 4 each time

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do that and show me

glacial widget
#

dnt u have to susbtituion rule

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and stuff

alpine oar
#

hmm?

glacial widget
#

its gonna taek forever

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(1/4)e^4x

alpine oar
#

what substitution rule

glacial widget
#

to intergrate that

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uhh

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u = 4x

alpine oar
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to integrate that

glacial widget
#

u' = 4

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dx = 1/4 du

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that one

alpine oar
#

uhh

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okay what I do is

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I put the e^4x

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and then divide by the differentiation of the power

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which is 4

glacial widget
#

☠️

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😭

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i think i may have to go to the TA because I think learning a whole other way of this is gonna harm me for my finals

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like if my professor wants to see this stupid box method

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i got all other 8 questions its just this one really messing me up

alpine oar
#

well yeah if it's gonna harm your finals to do it this way then yeah maybe not

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but it's just so much easier

glacial widget
#

I understand :(. and i respect u sm for trying to help me but i gotta go to the TA to learn the way he wants us to learn it which is so.. ugh

#

tysm ! tho

alpine oar
#

oh no problem at all

glacial widget
#

u gave me the right answer which led me in teh right direction so

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i appreicate it sm

alpine oar
#

I can link you a video in case you wanna learn the tabular method

glacial widget
#

Lol ill remember it before calc 2

alpine oar
#

alright

glacial widget
#

hopefully

alpine oar
#

have a good day/night!

glacial widget
#

ty1

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how do i mark as done

alpine oar
#

.close

glacial widget
#

.close

obtuse pebbleBOT
#
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burnt ruin
#

I need help with mathcad. I'm trying to plot a piecewise function and have the function peg out if it exceeds a max val or goes below a min. I have the piecewise itself working but I can't figure out why my other program isn't working

burnt ruin
obtuse pebbleBOT
#

@burnt ruin Has your question been resolved?

obtuse pebbleBOT
#

@burnt ruin Has your question been resolved?

obtuse pebbleBOT
#

@burnt ruin Has your question been resolved?

burnt ruin
#

Bump

burnt ruin
#

figured it out

#

range var was wrong

obtuse pebbleBOT
#

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coarse thicket
#

How do I tell if the coefficients of the sine or cosine term in a fourier series are zero or non zero?

gilded needle
#

can you give an example?

coarse thicket
#

f(x) = 0 for 0 <= x <= 3, 1 for 3 <= x < 6 where f(x) = f(x+6)

#

By looking at the graph of periods of a function similar to this how would I be able to tell the above?

gilded needle
#

one thing to observe is that if you subtracted a constant 1/2 from this function, it would be an odd function

#

therefore all the cosine coefficients (excluding n=0) would be zero

#

so the fourier series would be of the form 1/2 + sum(n=1 to infinity) b_n sin(omega n) for an appropriate choice of omega

coarse thicket
#

hmm i think i get it

#

what about a function that looks like 4 for 0 <= x < 3, or -4 for 3 <= x < 6 same f(x)=f(x+6)

gilded needle
#

same deal except the constant term would be 0 instead of 1/2

coarse thicket
#

why is constant term 0 here?

#

or wait i see it nevermind

#

thank you

#

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tidal relic
#

how do i do this

obtuse pebbleBOT
tidal relic
#

i only know u sub rule rn

fathom flicker
#

The binomial theorem is all you need here

high lily
#

id ibp this

fathom flicker
#

but maybe it'd be better to usub u=x+8 or ibp

#

(then u-8=x)

tidal relic
#

whats ibp

fathom flicker
#

integration by parts

#

but you likely haven't learned that yet

tidal relic
#

oh

tidal relic
#

wait

#

do i then do du - 8 = dx

timid silo
#

Pascal’s triangle

#

And distribute the x

#

😈

#

The do some power rules

#

That would go lit

#

In all seriousness I think setting u = x+8 gets you off and running

#

Wait

#

No I don’t think it does

tidal relic
#

i got to the integral of x(u)^8 dx and then

integral of x(u)^8 -8 du

#

idk how to get the X out

timid silo
#

Yea

#

You don’t know

#

Integration by parts

#

Correct?

#

(u-8)(u)^8du

#

Hmm

#

I wonder what we can with that

#

Perhaps multiply out the u^8

#

And go from there :P

tidal relic
#

ive literally only been taught u sub

#

ahhhhhhhhhh

timid silo
#

I think I have a rough idea of the answer

brave bramble
timid silo
#

He got it

tidal relic
brave bramble
#

Oh you might be missing that
x = u - 8

#

You can't leave an x in there after your u-sub

tidal relic
#

OHHH

#

(u-8)(u)^8 -8 du?

brave bramble
#

Wait where's the -8 from

tidal relic
#

du-8=dx

#

or is that wrong

#

is du=dx

#

okay

#

cuz i used x=u-8 on accident

#

and it confused me

brave bramble
#

∫ (u - 8)u⁸ du

tidal relic
#

i see

brave bramble
#

Which is easier to get than the original, for sure

tidal relic
#

so now

#

do i distribute

timid silo
#

That’s what I said earlier

tidal relic
#

and everyone else

#

thanks

#

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#
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dull void
#

how you solve this derivative

$e^{x^2}$

obtuse pebbleBOT
warm shaleBOT
#

odokawa

dull void
#

if you could provide me a rule or something it would be great

#

i have the rule

sage geode
#

Chain rule

dull void
#

why?

sage geode
#

Because you have a composition of two functions

dull void
#

there is a rule which say

#

ok

#

so it would be

#

$e^{x^2} . 2x$

#

@sage geode if not let me know

sage geode
#

What's the derivative of x^2?

dull void
sage geode
#

Right, so it's $e^{x^2} \cdot 2x$

warm shaleBOT
#

odokawa

#

A Lonely Bean

dull void
#

.close

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#
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dull void
#

.reopen

obtuse pebbleBOT
#

dull void
#

@sage geode what about if we have

#

$e^{x^2} . 2x$

warm shaleBOT
#

odokawa

dull void
#

and now we have to derivate it again

sage geode
#

Product rule and chain rule

obtuse pebbleBOT
#
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pure nymph
#

,rotate

obtuse pebbleBOT
warm shaleBOT
pure nymph
#

Guys how do I solve this?

#

,rotate

warm shaleBOT
obtuse pebbleBOT
#

@pure nymph Has your question been resolved?

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timid silo
#

What's the derivative of this function?

obtuse pebbleBOT
timid silo
#

I think it's -5

#

But according to my book, it should be 5

#

give us some information on what the letters are

#

are P_K and P,_D independent variables from each other?

#

yeah

#

it's an economic function

#

and I need to take the first derivative of the function

#

okay when you say "find the derivative of the this function" you are being ambiguous since you have to specify with respect to what also

#

alr, sorry

#

it could be with respect to P_K or P_D

#

hmm

#

if it is with respect to P_D, you treat P_K as constant and the answer is indeed 5

#

okay yes it is with respect to P_D then

#

treat P_K as a constant and differentiate

#

I get it

#

so if it would be /aP_K

#

it would have been -10

#

yes

#

alright

#

thank you a lot

#

.close

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mellow olive
#

I don't really understand where to start/how I can use double formula

mellow olive
#

just never see this layout of question before

shut lagoon
#

Use the fact that sin(π-x) = sin(x).

#

Start from sin(2π/5) and apply the double angle formula.

mellow olive
#

💀 OH WAIT

#

my bad

#

ik what u mean now

#

like pi/5 is theta

#

@shut lagoon

#

so im left with 2sin(pi/5) cos (pi/5)

#

thonk whats next

shut lagoon
#

Try the identity I gave you earlier.

shut lagoon
obtuse pebbleBOT
#

@mellow olive Has your question been resolved?

mellow olive
#

idk how to use t he identity

#

😭

#

im just not seeing it

shut lagoon
#

What is pi - pi/5?

mellow olive
#

pi4/5

#

OH

#

dang

#

💀

mellow olive
shut lagoon
#

Hum

#

Maybe

#

cos(x) = cos(2pi - x)

mellow olive
shut lagoon
#

Yes that will give you the first identity

mellow olive
#

what i don't really get is why you couldnt just stay with 2 sin pi/5 cos pi/5

shut lagoon
#

Because it asks to show that sin(2pi/5) = 2cos(pi/5)sin(4pi/5)

mellow olive
#

yes but if u didt know the idetity the u wouldnt rlly know what to do right

#

well at least in the textbook i didnt see that identity

#

oh wait i mean

#

not really in that unit

#

but yeah i get what u mean

#

thanks 😄

#

can i try part b and show u my work

mellow olive
#

@shut lagoon i thought that this was the identity so shouldn't the 4pi/7 be a negative and not a positive?

shut lagoon
#

It works with that one since it's squared

#

So the sign doesn't matter

mellow olive
#

oh alrihgt thanks bro

#

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#
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hollow igloo
#

$x + \frac{\pi}{6} = 3x,$
$x = \frac{\pi}{12}$

hollow igloo
#

but what about the others solutions?

#

this functiosn have different phase how do i calculate all of their solutions then?

warm shaleBOT
cunning breach
#

Two things:

  1. What is the domain?
  2. What angle is equivalent to cos(x)?
hollow igloo
#

domain is R

#

angle equalivent to cos(x) would be any $x + 2\pi k, k \in Z$

warm shaleBOT
hollow igloo
#

@cunning breach

#

but cos(3x) has different phase

#

so how do i calculate this

cunning breach
timid silo
#

Hi, can you please explain how to solve a problem like this? Step by step?

The call centre of a certain company receives an average of 30 calls per hour. The calls are independent of each other. 60% of the people who call the centre are men. The 100th person,
who calls the center gets a special reward from the company. Using CLV, calculate
the probability that

  1. there are at most 75 men among the 150 people calling the center,
  2. the waiting time for the caller(s) to receive the reward is at least 3 hours.
cunning breach
#

Sin, cos and tan have two quadrants with equivalent values.

hollow igloo
#

yes

#

cos have 1 and 4 quadrant the same

#

or x = -x

cunning breach
hollow igloo
#

$x + \frac{\pi}{6} = -3x$ but what about the phase?

warm shaleBOT
hollow igloo
#

this gives 2 solutions?

#

so know this is just $\frac{pi}{12} + 2\pik , k \in Z$? and the other solution with 2pik?

warm shaleBOT
#

Yanek
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

cunning breach
# warm shale **Yanek**

What do you mean by phrase? This gives x = pi/12 + k*pi, and so does the other set of solutions.

hollow igloo
#

so it doesn't matter that cos(3x) has phase of $\frac{2\pi k}{3}?$

warm shaleBOT
cunning breach
#

$$cos (x+\frac{\pi}{6}) = cos(3x)$$ $$=> x+\frac{pi}{6}=\pm 3x + k*2\pi$$

warm shaleBOT
hollow igloo
#

i see

#

ok so when i have 2 functions f(x) = f(y) that have different phase i should take only the bigger one?

cunning breach
#

I'm not quite following here.

hollow igloo
#

$cos(3(x + \frac{2\pi k}{3}))$

warm shaleBOT
hollow igloo
#

@cunning breach would it work the same with lets say cos(2x) = cos(3x + pi/6)?

#

2x = -+3x + pi/6 + 2pik?

cunning breach
warm shaleBOT
cunning breach
#

Try cos(2x) = cos(3x)

hollow igloo
#

i was talking about the phase if it should be something different than 2pik there

#

i just not sure

#

but i quess you are right

cunning breach
#

2pi is the same as 360 degrees, which is a full circle.

#

cos(0) = cos(2pi) = cos(4pi). If this is what you was wondering.

hollow igloo
#

yes, i know that, but the thing is the phase of cos(2x) is different than cos(x) and cos(3x)

cunning breach
#

You mind explaning what "phrase" is? I'm not native english, so I'm unfamiliar with some words.

hollow igloo
#

In physics and mathematics, the phase (symbol φ or ϕ) of a wave or other periodic function

    F
  

{\displaystyle F}

of some real variable

    t
  

{\displaystyle t}

(such as time) is an angle-like quantity representing the fraction of the cycle covered up to

 ...
#

im not native too so dont worry

#

wolfram alpha shows one solution that we didn't have

#

@cunning breach if you mind looking at that

cunning breach
#

Still don't get, if that's period, then it indeed would change, but you start with 2pi, since that a circle, else you need for a other persons explanation.
Speaking of wolframes three solutions, this might caused by + = +, + = -, - = +. You could try out.

hollow igloo
#

ok

#

thanks a lot for you time

cunning breach
#

Welcome.

obtuse pebbleBOT
#

@hollow igloo Has your question been resolved?

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next wagon
#

Hello, if the limite of a sequence function is +oo, does it imply that it’s inferior limit is +oo ?

fossil crag
#

If the lim exists then lim = liminf = limsup ;)

next wagon
#

J’osais pas te redemander des questions alala je t’aime tellement

#

Ah d’accord donc + et -oo inclu

#

Merci beaucoup ❤️

#

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marble jay
obtuse pebbleBOT
marble jay
#

can someone explain what the max(S_x,S_y)/min(S_x,S_y) means????

stark root
#

Can anyone can solve this sequence problem?

wanton hull
obtuse pebbleBOT
# stark root

Someone else is already using this help channel. If you need help with a question, please open your own help channel/thread (see #❓how-to-get-help for instructions).

stark root
#

Sorry

obtuse pebbleBOT
#

@marble jay Has your question been resolved?

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maiden sage
#

Hello, I really need your help I have been struggeling 2 hours on this. So I have a task that I need to complete for school. This is working with statistics of population and demographics.

So my problem:

I have found that the population in Malaysia is 32698,1 in 2022 (number 000') and that it is expected to reach 33379,5 in 2023.

In the population you have citizens and non-citizens. We have 30198,2 citizens and 2500,0 non-citizens in 2022. In 2023 it is expected to be 30415,3 citizens and 2964,2 non-citizens.

So that is a total increase of 2,083913132567% from 2022 -> 2023.
And for citizens an increase of 0,718917021544% from 2022 -> 2023.
And for non-citizens an increase of 18,568% from 2022 -> 2023.

So now if I calculate total population with a population growth of 2,08...%. Or I calculate the citizens and non-citizens with an population growth of 0.71% and 18,5% individually and add them up I get something completely different from the total.

How is this possible please help!

maiden sage
obtuse pebbleBOT
#

@maiden sage Has your question been resolved?

obtuse pebbleBOT
#

@maiden sage Has your question been resolved?

obtuse pebbleBOT
#

@maiden sage Has your question been resolved?

obtuse pebbleBOT
#

@maiden sage Has your question been resolved?

obtuse pebbleBOT
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autumn delta
#

can anyone help me with this

obtuse pebbleBOT
autumn delta
#

i dont get it at all

lone echo
#

post the instructions

autumn delta
#

my ad

#

bad

#

i just did the top function = -2 but i dont understand why it works

#

oh hold on

#

nvm

#

.close

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#
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autumn delta
obtuse pebbleBOT
autumn delta
#

i dont get this question

oak aurora
#

Do you want to try writing out the IVT theorem first?

autumn delta
#

i graphed it on desmos it's not a continious function?

oak aurora
#

Right so the question here is telling you that f(0)<10 and f(4)>10, so if we blindly apply IVT, we should have that there exists x in (0,4) such that h(x)=10

oak aurora
#

so the point of the question is to make sure you know that IVT is only true for continuous function

#

the function your working with here isn

autumn delta
#

Ohhhh okay thanks

#

.close

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#
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thin thistle
#

here we need to find f’(x)

obtuse pebbleBOT
thin thistle
#

and as i understand to do that, we need to confirm if it’s continuous then check for differentiation

#

i get how we proved its continuous

#

then we moved on to check for the differentiation of

  1. x≠0
  2. x=0
#

and again, we pretty much differentiated xsin(1/x) for the first term

oak aurora
#

are you sure lim xsin(1/x)=0?

thin thistle
#

but i dont get what we did for the second term

thin thistle
verbal prism
#

the second term, as in the differential for 0?

thin thistle
#

the differential for when x=0

#

yes

verbal prism
#

graph x = 0

#

what is the slope?

oak aurora
thin thistle
#

undefined

verbal prism
#

you can't differentiate it because of that

#

the top one is product rule, the dne is because it is undefined

#

DNE = Does Not Exist

thin thistle
#

but i meant about the take “because” part

#

that went into the technicalities

verbal prism
#

ah, okay

thin thistle
#

why did we use the limit as x approaches 0

#

and why did we put in it the evaluation of the first term

verbal prism
#

the 'because' part where they do the limit has a limit because we are dividing by 0

#

we can't divide by 0, and there will be a hole there

#

BUT if it approaches on both sides, it exists and we can pretend there is no hole

#

the -1/x(cos1/x) makes it necessary to do the limit there

thin thistle
#

well okay but then again

thin thistle
#

i mean why did we put it inside

verbal prism
#

ah, inside where, inside the cosine and sine?

#

sorry, I am confused as to what you are asking

oak aurora
#

the terms are within the limit

#

so we he doesn’t have to consider x=0

#

but anyway what is the definition of f’(0) @thin thistle

#

like in the most general sense, given some f(x)

thin thistle
#

limx -> 0 f(x) - f(0)/x - 0

oak aurora
thin thistle
#

are u asking me because ur confused or are u asking me to get me to arrive to a conclusion

#

because im getting more and more confused

oak aurora
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the latter

oak aurora
thin thistle
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to clear the confusion, my question is,

when we want to check for the differentiation in x=0, why are we using the limit? and why are we asking about the limit of that very specific term

oak aurora
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but at the same time note that the limit your taking is not f’(0).

thin thistle
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what is it then

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if thats not it

oak aurora
thin thistle
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but why

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if we’re talking about when x=0

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how is that any relevant

oak aurora
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Because the definition of f’(0) is about the limit of f(x)-f(0)/x-0 as x approaches 0

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As x approaches 0, x=/=0

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so f(x) is still just xsin(1/x)

verbal prism
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lusgnol you're confusing me too and I am in cal 3 🥵

thin thistle
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😭😭😭

oak aurora
verbal prism
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no, I am disagreeing with you on whether it is relevant to their question

thin thistle
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wait let me say something

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and correct me if im wrong

verbal prism
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they are just trying to find domain of something and confused as to why the limit is needed, I think

oak aurora
thin thistle
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the first term refers to the derivative when x≠0

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well when x≠0, x is just a constant

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and the derivative of any constant is 0

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so we’re asking for the limit of that derivative?

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to check for 0

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which clearly doesnt exist in that manner

verbal prism
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i am explaining this from a physics-applied-math viewpoint and not a pure-math-knowledge viewpoint BUT

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this is piecewise because that hole gets in our way

thin thistle
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yea

verbal prism
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so we fill in the hole with the value it approaches using a piecewise function

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HOWEVER the value that we use to fill it in was (likely, I haven't checked) acquired by taking the limit of f(x) approaching 0 when x!=0

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the f'(x) ALSO is the same function, but there still is a hole there. we can use that function to find the value of the hole and fill it in

oak aurora
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and why exactly are you filling in the hole?

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The question is asking for the derivative of the piecewise function

verbal prism
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well we want to know if there is anything there, so we take the derivative and the limit of that derivative as we approach the hole

verbal prism
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but we know that won't work because of the -1/x, we would be dividing by zero

thin thistle
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which brings me to my second question

verbal prism
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BUT even if there is no hole, taking the limit will get us the value at that point

thin thistle
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in that limit

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sin1/x is dne

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as x approaches 0

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i get it

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but why is -1/xcos1/x = 0

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using the squeeze theorem
-1<= cos1/x <=1

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1/x <= -1/xcos1/x <= -1/x

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shouldnt the limit for 1/x and -1/x be dne

verbal prism
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good point thinkies

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the limit of cos(x) is DNE because it doesn't approach anything

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the limit of -1/x is negative infinity because the divisor is so small it makes the number on top huge

thin thistle
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and 1/x is infinity

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the math isnt mathing

verbal prism
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ok the limit of 1/x approaches infinity so cos(1/x) should be DNE to my humble knowledge

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the fact that it is multiplied by -1/x shouldn't matter, DNE * infinity should be DNE

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lemme graph this

thin thistle
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i think ill just take it as a rule that the derivative of 0 is dne and call it a day

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my head hurts 😭

verbal prism
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well yeah the derivative of x = any constant is DNE because of the slope

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you can remember it because of the slope

thin thistle
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huh

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the derivative of any constant is just 0

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no?

verbal prism
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my calculus 1 education at my school is actually garbage

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but

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what I was taught is that they don't have a slope

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so you can just say it's 0

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but maybe I should not be peddling that around thinkies

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sorry if its y=0 then its a horizontal line

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so it is no slope

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but if its x = 0

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then it is a vertical line

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which makes more sense when you do 3D calculus

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so its 0 because the constant will always be y = 0 for you

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i am sorry for confusing you 😭

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it has been a while since cal 1

thin thistle
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lmao its alright

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thanks for ur time

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:D

verbal prism
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you're good

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are you still confused on the original part?

thin thistle
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no i think i get it now

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tysm :D

verbal prism
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honestly not sure why its approaching 0 and not DNE but maybe squeeze theorem will help

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you're welcome 👍

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im sorry lusgnol you are very good at math but my simple physicist brain can only math that makes physical sense to me

oak aurora
verbal prism
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🤔

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that looks like what he had

oak aurora
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im talking about the cos expression

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and i dont want to argue with you but your definition of filling holes to find the derivative is just not how derivatives are defined

verbal prism
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not what i said

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you fill holes to find the piecewise function's values at each point where the function itself does not suffice

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works well enough for me in applied math

oak aurora
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That’s my question to you

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his f’(0)

oak aurora
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derivatives refer to the slope

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you can fill in such that the piecewise function can be continuous

verbal prism
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I am not talking about the derivative, just the hole

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the derivative is the function in question there

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but I meant that for any function where we have holes we want to check out

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also his f'(0) should be undefined there i think

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and his derivative is right

oak aurora
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im talking about the expression itself

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the lim_{xapproaches 0} -1/xcos(1/x)+sin(1/x)

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is this f’(0)?

thin thistle
verbal prism
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it's f'(x) as x approaches 0

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but in lazy wording

oak aurora
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it is not

verbal prism
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hey man it's good enough for my professors

oak aurora
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f’(0)=limit as x approaches 0 of f(x)-f(0)/(x-0)

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which should be (xsin(1/x)-0)/(x-0)

thin thistle
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u mean f(x) - f(0) / (x-0)?

oak aurora
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yes

thin thistle
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wells thats the definition yes

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but what would u do after that

oak aurora
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not whatever your expression is there

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Likely for you calculus class, you can assume that limit of sin(1/x) as x approaches 0 is undefined

thin thistle
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which is xsin(1/x)/xsin(1/x)

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meaning undefined

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right?

oak aurora
thin thistle
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since that cancels out to 0/0

thin thistle
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but substitute x with xsin(1/x)

oak aurora
thin thistle
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oh right

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i divided by f(x) instead of x

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but yeah i get what ur trying to say

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but the limit in the picture is sent isnt talking about the definition

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its using another logic

oak aurora
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yes your f’(0) comes from nowhere..

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it’s possible for function to be differentiable everywhere but the derivative to not be continuous

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your trying to test for continuity of derivative at 0 but that’s simply not the same as finding f’(0)

thin thistle
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that is if the derivative of any constant is 0, and if the derivative of any constant thats not 0 in that function -1/x * cos(1/x) + sin(1/x)

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then the derivative of 0 would be the limit of -1…

oak aurora
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you should not be caring about the derivative of constants

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because the f’(0) is about the behaviour of the function as it approaches 0

thin thistle
oak aurora
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i’m talking about the continuity of the derivative

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not the continuity of the original function

oak aurora
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the final expression you have in your original working is about the continuity of the derivative right?

thin thistle
# oak aurora

well i understand my professor’s way but jts a pain in the ass, ur definition made it click easier

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now i can use the same way of thinking for all similar scenarios

thin thistle
oak aurora
thin thistle
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its about the differentiation of x=0

oak aurora
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yes and i’m trying to tell you that your final expression is not the derivative of 0.