Prove the Identity $$\sin ^ { 3 } 3 x = \frac { 1 } { 2 } ( \sin 3 x ) ( 1 - \cos 6 x )$$

Prove the identity.
- $$\sin ^ { 3 } 3 x = \frac { 1 } { 2 } ( \sin 3 x ) ( 1 - \cos 6 x )$$