>    restart;

>    with(plots):

>    f:= (x,y)->x*y^2 + 2*y + x^2*y;

f := proc (x, y) options operator, arrow; x*y^2+2*y+x^2*y end proc

>    plot3d(f(x,y), x=0..2, y=0..1, axes=boxed, title="(14.8) Example 3");

[Maple Plot]

>    g:=(r,phi)->r*(1-r)*sin(phi) + 2/3*cos(2*phi);

g := proc (r, phi) options operator, arrow; r*(1-r)*sin(phi)+2/3*cos(2*phi) end proc

>    plot3d(g(r,phi), r=0..1, phi=0..2*Pi, axes=boxed, title = "Example 4");

[Maple Plot]

>    plot(g(0.5,phi), phi=0..2*Pi);

[Maple Plot]

>