> N[5]:=(xi,eta) -> (1-xi^2)*(1-eta)/2;

                                             2
             N[5] := (xi, eta) -> 1/2 (1 - xi ) (1 - eta)

> plot3d(N[5],-1..1,-1..1,grid=[15,15],axes=boxed,scaling=constrained,
> style=patch,orientation=[-60,60]);

> 
> 
