Find the Specified Quantity $y = 3 \cos \left( 3 x + \frac { \pi } { 2 } \right)$

Multiple Choice

Find the specified quantity.
-Find the period of $y = 3 \cos \left( 3 x + \frac { \pi } { 2 } \right)$ .

A) $\frac { \pi } { 2 }$
B) $\pi$
C) 3
D) $\frac { 2 \pi } { 3 }$