I want to calculate this double integral using Mathematica:
$$\iint_D x^3 y^3 \ln(1+x^2+y^2) \, \mathrm{d}x \, \mathrm{d}y,$$
where
$$D=\left\{ (x,y): x^2 + y^2 \leqslant 4, \; x,y \geqslant 0 \right\}.$$
I know how to calculate a definite double integral in Mathematica, but I am not sure how to do it with region $D$.