Integral of $$$\frac{x^{3}}{\sqrt{a^{2} - x^{2}}}$$$ with respect to $$$x$$$

The calculator will find the integral/antiderivative of $$$\frac{x^{3}}{\sqrt{a^{2} - x^{2}}}$$$ with respect to $$$x$$$, with steps shown.

Find $$$\int \frac{x^{3}}{\sqrt{a^{2} - x^{2}}}\, dx$$$.