Primitive of Sine of a x over Sine of a x plus phi

Theorem

 * $\displaystyle \int \frac {\sin a x \ \mathrm d x} {\sin \left({a x + \phi}\right)} = \frac x {\cos \phi} - \tan \phi \int \frac {\cos a x \ \mathrm d x} {\sin \left({a x + \phi}\right)} + C$