> N[3]:=(xi,eta) -> -(1+xi)*(1-9*xi^2)*(1+eta)*eta/32;

                                                 2
    N[3] := (xi, eta) -> -1/32 (1 + xi) (1 - 9 xi ) (1 + eta) eta

> plot3d(N[3],-1..1,-1..1,grid=[15,15],axes=boxed,scaling=constrained,
> style=patch,orientation=[-60,60]);

> 
> 
