Change the Cartesian integral into an equivalent polar integral. Then evaluate the polar integral.

${\displaystyle \underset{0}{\overset{3}{}}}{\displaystyle \underset{0}{\overset{y}{}}}xdxdy$

Change the Cartesian integral into an equivalent polar integral.

${\displaystyle \underset{0}{\overset{3}{}}}{\displaystyle \underset{0}{\overset{y}{}}}xdxdy={\displaystyle \underset{\frac{}{4}}{\overset{\frac{}{2}}{}}}{\displaystyle \underset{0}{\overset{\frac{3}{sin}}{}}}{r}^{2}cosdrd$

$($Type exact answers, using $$ as needed.$)$

The value of the double integral is $$

$($Type an integer or a simplified fraction.$)$