Question

Sin a_____=1/2 [sin (a + b) + sin (a - b)]

Answer 1

`\textbf{A.} \cos b`

Explanation:

`\frac 12 \left[\sin(a+b)+\sin(a-b) \right]\\\\\\=\frac 12\left[ 2 \sin a \cos b\right]\\\\\\=\sin a \cos b`