#### Answer

Identity for $\sin \left( C+D \right)$ is expressed as $\sin C\cos D+\cos C\sin D$.

#### Work Step by Step

From the sum formula of sines, the sine of the sum of two angles, say A and B, is expressed as,
$\sin \left( A+B \right)=\sin A\cos B+\cos A\sin B$
Thus, for angles C and D,
$\sin \left( C+D \right)=\sin C\cos D+\cos C\sin D$