Basic u subs will not work too well for this. It is not easily doable by
elementary means. That is why you found it in terms of gamma and what not.
If you are studying calculus, perhaps you mean
Two entirely different animals.
That is probably the case.
Go to the Integrator and check it out at http://integrals.wolfram.com/index.jsp
Type in sin[x^3] and it will show you it ain't pretty. That is why I think it is the other.