Primitive of Secant of a x/Tangent Form

Theorem

 * $\ds \int \sec a x \rd x = \frac 1 a \ln \size {\map \tan {\frac \pi 4 + \frac {a x} 2} } + C$

where $\map \tan {\dfrac \pi 4 + \dfrac {a x} 2} \ne 0$.

Also see

 * Primitive of $\csc a x$: Tangent Form