# Reasonably simple integral

1. Oct 30, 2009

### henryc09

1. The problem statement, all variables and given/known data
1. Evaluate:
$$\oint cos^2(x)dx$$

Using two different methods

2. Relevant equations

3. The attempt at a solution
I have done it making the substitution of cos^2(x) = (1 + cos(2x))/2 but don't see how you can do this another way. Integration by parts doesn't seem to work and nor does substitution as far as I'm aware. Any ideas?

2. Oct 30, 2009

### Seannation

You could maybe do something with this:

$$cos^2(x) + sin^2(x) = 1$$

3. Oct 30, 2009

### Jasso

Integration by parts does indeed work on this integral, you just have to know where to use your trig identities as Seannation was hinting at.

4. Oct 30, 2009

### henryc09

Ah ok I've got it now, thanks!