Question

Write the expression as the sine, cosine, or tangent of an angle.

cos 9x cos 6x - sin 9x sin 6x

O cos 3x
O sin 15x
O cos 15x
O sin 3x

Answer 1

Step-by-step explanation:

cos 9x cos 6x - sin 9x sin 6x = cos (9x+6x)

= cos 15x