помогите решить cos2x-cosxcos3x=0

cos2x-cosx=cos3x cos2x = cos3x + cosx cos2x = 2cos2x * cosx cos2x(cosx - 1/2) = 0 cos2x = 0 2x = pi/2 + k*pi x = pi/4 + k*pi/2 cosx = 1/2 x = +-pi/3 + 2 k*pi