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

Theorem

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

Also see

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