Some Surfaces
sombrero
> plot3d(sin(sqrt(x^2+y^2))/sqrt(x^2+y^2),x=-10..10,y=-10..10);
> plot(sin(sqrt(x^2))/sqrt(x^2),x=-10..10);
monkey saddle
> plot3d(x*(x^2-y^2),x=-3..3,y=-3..3,orientation=[50,75]);
dog saddle
> plot3d(x*y*y*(x^2-y^2),x=-3..3,y=-3..3,orientation=[50,75]);