Verify the identity. (Simplify at each step.) 3 cos(x + y) cos(x - y) = 3 cos(x) - 3 sin(y) 3 cos(x + y) cos(x - y) 3 (cos(x) cos(y) - ( = 3 cos(x) cos(y) - 3 sin(x) = 3 cos(x) (1 - = 3 cos(x) - 3 cos(x)( = = 3 cos (x) - = 3 cos(x) - 3 sin(y) ) ]) - ( [ 3 sin(x) n (x) (L 3 sin(x) (cos(x) + sin(x)) ) + sin(x)sin(y))