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

Answer:
Step-by-step 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