#Trig substiiton using x =asina

56 messages · Page 1 of 1 (latest)

cerulean fog
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Hey i have tried doing this problem and am having problem and the answer in the back of book is a number since its a definite integral bbut sofar I have integral of integral of ( 3 - 6sin(theta) 3 cos(theta) d(theta) )

ember tapirBOT
cerulean fog
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hold up ill try write i there

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idk i def did something wrong because usually your meant to sub in 1-sin^2x

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0but how do you do that with numbers infront

woven shuttle
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Take 4 common and apply this formula

Then you can simply put the limits

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Or if you want to derive it

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Substitute x as 3/2sin(theta)

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After taking 4 common

cerulean fog
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why 3/2

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ohh

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nvm

woven shuttle
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U need to make the coeff of x^2 1

cerulean fog
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wait

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how does the 3/2 cancel

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i get sqrt( 9 - 4(3/2sin(theta)^2 3/2cos(theta)d(theta)

woven shuttle
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U need to take 4 common first

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It will be 9/4 - 9/4 sin2(theta)

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Take 4 out of the root

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Out of the integral entirely

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I'm prob sure there is derivation of this formula on the internet

cerulean fog
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right

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ill have a look

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But otherwise that makes sense

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how it works

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tysm!

fervent topaz
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3(theta+cos(2theta)/2)+C

woven shuttle
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C is not necessary

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This is definite integ

fervent topaz
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That's not what I see

cerulean fog
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no that was very wrong

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ohh one question

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is changing limits the same when doing u sub

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just put in the limits into the x equation and use those?

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or do you have to substitute in theta again

cerulean fog
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wait shouldnt it be sin

fervent topaz
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there u go

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sorry i was playing 2k lol

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was doing mental math

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this is easy stuff

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use u substitution

fervent topaz
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or in this case theta domain instead of x

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but this problem is a indifinite integral

fervent topaz
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here u go

cerulean fog
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but right this makes sense thanks so much for writing it out

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really appreciate it!

fervent topaz
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Your welcome

cerulean fog
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.solved