int (x^3 - 3) * cos x dx = int (x^3 - 3) d(sin x) =
= (x^3 - 3) * sin x - int sin x d(x^3 - 3) = (x^3 - 3) * sin x - int 3 * x^2 * sin x dx =
= (x^3 - 3) * sin x - 3 * int x^2 * sin x dx = (x^3 - 3) * sin x - 3 * int x^2 d(-cos x) dx =
= (x^3 - 3) * sin x + 3 * int x^2 d(cos x) dx =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 3 * int cos x d(x^2) =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 3 * int 2 * x * cos x dx =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 6 * int x * cos x dx =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 6 * int x d(sin x) =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 6 * x * sin x + 6 * int sin x dx =
= (x^3 - 3) * sin x + 3 * x^2 * cos x - 6 * x * sin x - 6 * cos x + C