PLEASE HELP ME WITH THIS PROBLEM

Question

3 cos(1.5x)cos(0.5x)

this can be written as the sum of sine and/or cosine function.

Answer 1

Hi,

you need to Know this property : cos a * cos b = 1/2 [ cos( a + b ) + cos ( a- b) ]

3 cos(1.5x)cos(0.5x) = 3 * 1/2 * [ cos ( 1.5x + 0.5x) + cos ( 1.5x - 0.5x) ]

= 3/2 [ cos(2x) + cos (x) ]

I hope it was useful,

Minoo