Question

HELPPPP Cos x cosy = 1/2(sin (x+y)+ sin (x-y)) true or false

Answer 1

Explanation:

REcall that sin(a+b) = sin(a)cos(b)+cos(a)sin(b). Then

sin(a+b)+sin(a-b) = sin(a)cos(b)+cos(a)sin(b) + sin(a)cos(b) -cos(a)sin(b) = 2sin(a)cos(b). Then

sin(a)cos(b) = (1/2)(sin(a+b)+sin(a-b))

So it is false