How do you find this integral?

[asap9993]

Homework Statement

the problem is

Find the antiderivative of 1/(1 + cos(x))

Homework Equations

The Attempt at a Solution

I think it requires a trick, but I can't figure it out.

 

[lanedance]

is it a definite integral?

 

[ehild]

Use the relation between cos(x/2)and cos(x).

ehild