Question

Sin (x+y) . sin (x-y) = . . . .

Answer 1

Verified answer

TriGonoMetRi

sin (x + y) . sin (x - y)
= -1/2 (cos (x + y + x - y) - cos (x + y - x + y)
= -1/2 (cos 2x - cos 2y)
= -1/2 ((2cos² x - 1) - (2cos² y - 1))
= cos² y - cos² x