Write cos (10x) cos (2x) + sin (10x) sin (2x) as a single trigonometric function.
A) sin 8x
B) cos 8x
C) sin 12x
D) cos 12x

Question

Quizplus · Accepted Answer

This expression can be simplified using the trigonometric identity for the cosine of a difference, which states that cos(A - B) = cos A cos B + sin A sin B. Applying this identity to cos(10x) cos(2x) + sin(10x) sin(2x) results in cos(10x - 2x) = cos(8x), making the correct answer cos 8x.

Write Cos (10x) Cos (2x) + Sin (10x) Sin (2x)