Solve the Equation in the Interval $$\left[ 0 ^ { \circ } , 360 ^ { \circ } \right)$$

Multiple Choice

Solve the equation in the interval $$\left[ 0 ^ { \circ } , 360 ^ { \circ } \right)$$ ) . Give solutions to the nearest tenth, if necessary.
- $2 \cos ^ { 3 } \theta = \cos \theta$

A) $\left\{ 90 ^ { \circ } , 270 ^ { \circ } \right\}$
B) $\left\{ 45 ^ { \circ } , 135 ^ { \circ } , 225 ^ { \circ } , 315 ^ { \circ } \right\}$
C) $\varnothing$
D) $\left\{ 45 ^ { \circ } , 90 ^ { \circ } , 135 ^ { \circ } , 225 ^ { \circ } , 270 ^ { \circ } , 315 ^ { \circ } \right\}$