Evaluate: `int(sinx)/(sin(x-a))\ dx`

Explanation

`frac{sin x}{sin (x-a)}`

Let `x-a=t Rightarrow d x=d t`

`int frac{sin x}{sin (x-a)} d x=int frac{sin (t+a)}{sin t} d t`

`=int frac{sin t cos a+cos t sin a}{sin t} d t `

`=int(cos a+cot t sin a) d t `

`=t cos a+sin a log |sin t|+C_{1} `

`=(x-a) cos a+sin a log |sin (x-a)|+C_{1}`

`=x cos a+sin a log |sin (x-a)|-a cos a+C_{1} `

...