Find the Derivative of F(x)= Sin (7x)· Sin (8x) $7 \cos ( 8 x ) \sin ( 7 x ) - 8 \cos ( 7 x ) \sin ( 8 x )$

Multiple Choice

Find the derivative of f(x) = sin (7x) · sin (8x) .

A) $7 \cos ( 8 x ) \sin ( 7 x ) - 8 \cos ( 7 x ) \sin ( 8 x )$
B) $7 \cos ( 8 x ) \sin ( 7 x ) + 8 \cos ( 7 x ) \sin ( 8 x )$
C) $8 \cos ( 8 x ) \sin ( 7 x ) - 7 \cos ( 7 x ) \sin ( 8 x )$
D) $8 \cos ( 8 x ) \sin ( 7 x ) + 7 \cos ( 7 x ) \sin ( 8 x )$