Write the Product as a Sum or Difference of Trigonometric $\cos 38 ^ { \circ } \sin 23 ^ { \circ }$

Write the product as a sum or difference of trigonometric functions.
- $\cos 38 ^ { \circ } \sin 23 ^ { \circ }$

A) $\frac { 1 } { 2 } \left( \cos 61 ^ { \circ } + \cos 15 ^ { \circ } \right)$
B) $\frac { 1 } { 2 } \left( \cos 61 ^ { \circ } - \cos 15 ^ { \circ } \right)$
C) $\frac { 1 } { 2 } \left( \sin 61 ^ { \circ } - \sin 15 ^ { \circ } \right)$
D) $\frac { 1 } { 2 } \left( \sin 61 ^ { \circ } + \sin 15 ^ { \circ } \right)$