Primitive of Reciprocal of Square of 1 plus Cosine of a x

Theorem

 * $\displaystyle \int \frac {\mathrm d x} {\left({1 + \cos a x}\right)^2} = \frac 1 {2a} \tan \frac {a x} 2 + \frac 1 {6 a} \tan^3 \frac {a x} 2 + C$

Also see

 * Primitive of $\dfrac 1 {\left({1 + \sin a x}\right)^2}$