Express the Sum or Difference as a Product of Sines $\cos ( 6 \theta ) + \cos ( 4 \theta )$

Multiple Choice

Express the sum or difference as a product of sines and/or cosines.
- $\cos ( 6 \theta ) + \cos ( 4 \theta )$

A) $2 \cos ( 5 \theta ) \sin \theta$
B) $2 \cos ( 5 \theta ) \cos \theta$
C) $2 \cos ( 5 \theta )$
D) $2 \sin ( 5 \theta ) \sin \theta$