Can someone point me in the right directon

[gona]

the problem is to intigrate cot$$^{2}$$x

now i kow that cot$$^{2}$$x = $$\frac{cos^{2}x}{sin^{2}x}$$

now iv tryed various substitutions like usig the power reducton forumulas...
and then using double angle substiutions but nothin seems to work for me

so i was wondering if someone could just tell me where to start so i can
finish this question... been trying to figure this out for like a hour now

thanks in advance

 

[HallsofIvy]

Use the identities 1+ cot²(x)= csc²(x) so that cot²(x)= csc²(x)- 1. Since you know that the derivative of cot(x) is csc²(x), that should be easy.

 

[gona]

Wow that was suprisingly simple thank a lot yea i didnt know about that identity that was the first time iv used it. Thnx a lot great help

 

[Kurdt]

There are many pages that list trig identities. Whenever I work with trig functions I always just open a page and have a look at how the functions in the question are related. There are loads of pages, but I do like wikipedias as it has a list of the 6 trig functions in terms of the others which is very handy for some integration questions when trig substitution is needed.

http://en.wikipedia.org/wiki/Trigonometric_identity

 

[gona]

Wow very nice I am going to bookmark this page right away thnx again!