1)

If $\int_{}^{}\frac{\sin x}{\sin (x - \alpha)}dx = Ax + B\log_{}{\sin (x - \alpha)}+C$ then value of (A,B) is


A) $(-\cos\alpha,\sin\alpha)$

B) $(\cos\alpha,\sin\alpha)$

C) $(-\sin\alpha,\cos\alpha)$

D) $(\sin\alpha,\cos\alpha)$

Answer:

Option B

Explanation:

$\int_{}^{}\frac{\sin x}{\sin (x - \alpha)}dx$

= $\int_{}^{}\frac{\sin (x-\alpha+\alpha)}{\sin (x - \alpha)}dx$

=$\int_{}^{}\frac{\sin (x-\alpha)\cos\alpha+\cos (x-\alpha)\sin\alpha}{\sin (x - \alpha)}dx$

=$\int_{}^{}\left\{\cos\alpha+\sin\alpha\cot(x - \alpha)\right\}dx$

= $(\cos\alpha)x+(\sin\alpha)\log_{}{\sin(x-\alpha)}+C$

A = $\cos\alpha$ B = $\sin\alpha$