\(\rm \displaystyle\int \frac{dx}{\sin (x−a) \sin (x−b)}\) =
1
sin (b − a) log \(\rm \left|\frac{\sin (x−b)}{\sin (x−a)}\right|\) + C
2
cosec (b − a) log \(\rm \left|\frac{\sin (x−a)}{\sin (x−b)}\right|\) + C
3
cosec (b − a) log \(\rm \left|\frac{\sin (x−b)}{\sin (x−a)}\right|\) + C
4
sin (b − a) log \(\rm \left|\frac{\sin (x−a)}{\sin (x−b)}\right|\) + C