Помогите с математикой !!!sin^3 x - sinx - cosx = 0

(sin(x))^3 - sin(x) - cos(x) = 0
sin(x) * ((sin(x))^2 - 1) - cos(x) = 0
sin(x) * ((1 - (cos(x))^2) - 1) - cos(x) = 0
sin(x) * (cos(x))^2 + cos(x) = 0
cos(x) * (sin(x) * cos(x) + 1) = 0

sin(x) * cos(x) = -1
0.5 * sin(2*x) = -1
sin(2*x) = -2
решения нет

остается:
cos(x) = 0