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qzack96

Member

Registered: 2009-07-29

Posts: 1

Trig substitution.. Please HELP !

Please write the u and du values for each. I'd really appreciate it !

1) Integrate (X*sq(x^2 + 1)) dx

2) Integrate (x/ (x^2 + 1) ) dx

3) Integrate (x/ (x^2 + 1)^2 ) dx

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Trig substitution.. Please HELP !

Hi qzack96;

Your title says trig substitution but a standard substitution is the right way to go here, so that is what I have done. If this is OK then:

For 2)

say

Last edited by bobbym (2009-07-29 21:29:36)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

riad zaidan

Guest

Re: Trig substitution.. Please HELP !

Hi,
you can multiply both numerator and denominator by 2 , then the integral is

(1/2)ln (x^2+1)+C
with best wishes
Mr   riad zidan