# Trigonometric identities for integral problem

1. Oct 20, 2008

### student85

1. The problem statement, all variables and given/known data
I have this integral to solve:
$$\int$$ $$\frac{ab}{a^2 cos^2 t + b^2 sin^2 t}$$ dt

The limits are 0 to 2*pi.

2. Relevant equations

3. The attempt at a solution
I've tried using trigonometric identities, trigonometric substitution... and many kinds of algebraic manipulations but I can't do it! I'm beginning to think it can't be done analytically but I doubt it because my professor wants us to prove it is equal to something else which I found is 2*pi. I used my calculator to do the integration and I did get 2*pi, so at least I know what it is equal to. However I don't seem to get anywhere trying to solve it. Please help!

Thanks.

2. Oct 20, 2008

### jhicks

Re: Integral!

It looks like latex is acting up (maybe just for me?). You might want to just write out the code. Most of us will be able to read it anyhow.

3. Oct 20, 2008

### student85

Re: Integral!

I think if you click over the red text you see the latex code. Anyway here it is...
So it's an integral of: {ab} / {a^2 cos^2 t + b^2 sin^2 t} with respect to t.
From t=0 to 2*pi

4. Oct 21, 2008

### student85

Re: Integral!

Nevermind, I solved the problem.