Integration question give me a very quick ans?

Question

8cos^3x.sin 3x. dx

Answer 1

I don´t know to what exponent is cos 3x raised but in any case if we have
8Int cos^n 3x *sin 3x dx .If you call cos 3x =z ,-3sin3x dx = dz
and the integral becomes
-8/3 Int z^n dz = -8/3*(1/n+1)cos^(n+1) 3x +C