Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
Express the product as a sum containing only sines or cosines.
- $\sin ( 4 \theta ) \sin ( 6 \theta )$

A) $\sin ^ { 2 } \left( 24 \theta ^ { 2 } \right)$
B) $\frac { 1 } { 2 } [ - \cos ( 2 \theta ) - \cos ( 10 \theta ) ]$
C) $\frac { 1 } { 2 } [ \cos ( 2 \theta ) - \cos ( 10 \theta ) ]$
D) $\frac { 1 } { 2 } [ \cos ( 10 \theta ) - \sin ( 2 \theta ) ]$