# Integration of Cos Squared x

In this tutorial we shall derive the integral of cosine squared x.

The integration is of the form

This integral cannot be evaluated by the direct formula of integration, so using the trigonometric identity of half angle ${\cos ^2}x = \frac{{1 + \cos 2x}}{2}$, we have

Using the integral formula $\int {\cos kxdx = \frac{{\sin kx}}{k} + c}$, we have