Find the Exact Solution of the Equation $2 \cos ^ { - 1 } x = \pi$

Multiple Choice

Find the exact solution of the equation.
- $2 \cos ^ { - 1 } x = \pi$

A) $x = 0$
B) $x = 1$
C) $x = \frac { 3 \pi } { 2 }$
D) $x = \frac { \pi } { 2 }$