Express the Product as a Sum Containing Only Sines or Cosines

Multiple Choice

Express the product as a sum containing only sines or cosines.
- $$\cos \frac { 11 \theta } { 2 } \cos \frac { \theta } { 2 }$$

A) $\frac { 1 } { 4 } \cos ^ { 2 } ( 5 \theta )$
B) $\frac { 1 } { 4 } [ \cos ( 6 \theta ) - \sin ( 4 \theta ) ]$
C) $\frac { 1 } { 2 } [ \cos ( 2 \theta ) + \cos ( 3 \theta ) ]$
D) $\frac { 1 } { 2 } [ \cos ( 3 \theta ) - \sin ( 2 \theta ) ]$