Express the Product as a Sum or Difference $\cos 3 x \cos 2 x$

Multiple Choice

Express the product as a sum or difference.
- $\cos 3 x \cos 2 x$

A) $\frac { 1 } { 2 } ( \cos x + \cos 5 x )$
B) $\frac { 1 } { 2 } ( \cos 5 x - \sin x )$
C) $\frac { 1 } { 2 } ( \cos 5 x - \cos x )$
D) $\cos ^ { 2 } 6 \mathrm { x } ^ { 2 }$