int sin^3 x dx = int sin^2 x * sin x dx = int sin^2 x d(-cos x) = -int sin^2 x d(cos x) =
= -int (1 - cos^2 x) d(cos x) = | cos = t | = -int (1 - t^2) dt = -(t - 1/3 * t^3) + C =
= -t + 1/3 * t^3 + C = | t = cos x | = 1/3 * cos^3 x - cos x + C