> N[9]:=(xi,eta)->(1-xi^2)*(1-eta^2);

                                          2          2
              N[9] := (xi, eta) -> (1 - xi ) (1 - eta )

> plot3d(N[9],-1..1,-1..1,grid=[20,20], axes=boxed, scaling=constrained,
> style=patch,orientation=[-60,60]);

> 
> 
