Question

2cos(Х+60)соs3x=cos(x+60)

Answer 1

$2 cos (x+60) cos 3x=cos(x+60) \ 2cos3x = frac{cos (x+60)}{cos (x+60)} = 1\ cos3x = frac{1}{2} \ 3x = pm arccosfrac{1}{2} + 2 pi n\ 3x_1 = arccosfrac{1}{2} + 2 pi n\ 3x_1 = frac{ pi}{3} + 2 pi n\ x_1 = frac{ pi }{9} + frac{2}{3} pi n\ 3x_2 = -arccosfrac{1}{2} + 2 pi n\ 3x_2 = -frac{ pi}{3} + 2 pi n\ x_2 = - frac{ pi }{9} + frac{2}{3} pi n$