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.
Complete the identity.
- $\sin \theta [ \sin ( 2 \theta ) + \sin ( 4 \theta ) ] = ?$

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