# How do you find the integral of int cos^2theta?

Sep 26, 2015

Use the double angle formula for cosine to reduce the exponent.

#### Explanation:

$\cos \left(2 \theta\right) = 2 {\cos}^{2} \theta - 1$

So ${\cos}^{2} \theta = \frac{1}{2} \left(1 + \cos \left(2 \theta\right)\right)$

Hence the integral is

int cos^2theta d(theta)=int 1/2*(1+cos2theta) (d theta)= theta/2+1/4*sin2theta+c