INtegration by substitution followed by parts:

1. Feb 17, 2007

O.J.

... of (x tan^2 x). i dunno how to do it. pls help

2. Feb 17, 2007

cristo

Staff Emeritus
Well, what have you tried? This is clearly homework! Try writing tanx in terms of sinx and cosx.

3. Feb 17, 2007

O.J.

i tried that. i even tried using trig identities for the expansion of tan^2 but i got no where. im lost...

4. Feb 17, 2007

O.J.

any ideas?

5. Feb 17, 2007

ChaoticLlama

this is by-parts integration because you have two functions multiplied by each other.
But before you do that you should use a trig identity (think of an identity which will give you an easily integratable trig function).

6. Feb 18, 2007

cristo

Staff Emeritus
7. Feb 18, 2007

Gib Z

Good work though :P

8. Feb 18, 2007

cristo

Staff Emeritus
Hint: Do you know an identity for tan2x in terms of, say, sec2x?

Try using this then integrate by parts. Post your work so we can help you.