Question

(sin 7x + sin 5x) + (sin 9x + sin 3x)/
(cos 7x + cos 5x)+(cos 9x + cos 3x)= tan 6x​

Answer 1

use sinx + siny = 2sin(x+y/2)cos(x-y)2

cosx + cosy = 2cos(x+y/2)cos(x-y)/2