Express the Product as a Sum or Difference $\cos 5 x \cos 8 x$

Multiple Choice

Express the product as a sum or difference.
- $\cos 5 x \cos 8 x$

A) $\frac { 1 } { 2 } ( \cos 3 x + \cos 13 x )$
B) $\frac { 1 } { 2 } ( \cos 13 x - \sin 3 x )$
C) $\frac { 1 } { 2 } ( \cos 13 x - \cos 3 x )$
D) $\cos ^ { 2 } 28 x ^ { 2 }$