1. ## Integration question

Hi, how do I integrate this?

Int 1/(1 + cos 2x) dx

Thanks

2. Originally Posted by chancey
Hi, how do I integrate this?

Int 1/(1 + cos 2x) dx

Thanks
remember, $\cos 2x = 2 \cos^2 x - 1$

3. Yeah, but I still can't solve it with that?

4. Originally Posted by chancey
Hi, how do I integrate this?

Int 1/(1 + cos 2x) dx

Thanks
Originally Posted by Jhevon
remember, $\cos 2x = 2 \cos^2 x - 1$
What he's up to is
$\int \frac{dx}{1 + cos(2x)} = \int \frac{dx}{1 + 2cos^2(x) - 1} = \int \frac{dx}{2cos^2(x)}$

$= \frac{1}{2} \int sec^2(x) dx$

Do you know of any function who's derivative is $sec^2(x)$?

-Dan

Edit: Jhevon politely and quietly PMed me that I had made a mistake and left a "2" out. I have fixed this mistake.