> N[7]:=(xi,eta)->(1-xi^2)*(1+eta)*eta/2;

                                           2
           N[7] := (xi, eta) -> 1/2 (1 - xi ) (1 + eta) eta

> plot3d(N[7],-1..1,-1..1,grid=[20,20], axes=boxed, scaling=constrained,
> style=patch);

> 
> 
