How to deal with multiplication inside of integral? I have an undefined integral like this:
\begin{aligned}
\ \int x^3 \cdot \sin(4+9x^4)dx
\end{aligned}
I have to integrate it and I have no idea where to start. I have basic formulas for integrating but I need to split this equation into two or to do something else.

Hint:
$$\begin{eqnarray*}
(\cos (u(x)))^{\prime } &=&-\sin (u(x))u^{\prime }(x)\qquad\text{(by the chain rule)} \\
&\Leftrightarrow &\int \sin (u(x))u^{\prime }(x)dx=-\cos (u(x))+\text{Const.}
\end{eqnarray*}$$
