Find the Zeros of the Function in the Interval $[-2 \pi, 2 \pi]$

Multiple Choice

Find the zeros of the function in the interval $[-2 \pi, 2 \pi]$ .
- $$f ( x ) = \frac { 1 } { 2 } \cos 2 x$$

A) $\pm \frac { \pi } { 2 } , \pm \frac { 3 \pi } { 2 }$
B) $\pm \pi , \pm 3 \pi$
C) $0 , \pm \frac { \pi } { 4 } , \pm \frac { 3 \pi } { 4 }$
D) $\pm \frac { \pi } { 4 } , \pm \frac { 3 \pi } { 4 } , \pm \frac { 5 \pi } { 4 } , \pm \frac { 7 \pi } { 4 }$