$29-31=$ Use polar coordinates to find the limit$.[$If $(r,)$ are polar coordinates of the point $(x,y)$ with $r0,$ note that $r{0}^{}$as $(x,y)(0,0).]$

$29.\underset{(x,y)(0,0)}{lim}\frac{x^3{y}^3}{x^2{y}^2}$

$30.\underset{(x,y)(0,0)}{lim}(x^2{y}^2)ln(x^2{y}^2)$

$31.\underset{(x,y)(0,0)}{lim}\frac{e^{-x^2{y}^2}-1}{x^2{y}^2}$