Show That the Equation Is Not an Identity by Finding $\cos x - \cos x \sin x = \cos ^ { 3 } x$

Multiple Choice

Show that the equation is not an identity by finding a value of x for which both sides are defined but not equal.
- $\cos x - \cos x \sin x = \cos ^ { 3 } x$

A) $\frac { \pi } { 4 }$
B) $\frac { \pi } { 2 }$
C) $\pi$
D) 0