> N[11]:=(xi,eta) -> 9*(1-xi)*(1-eta^2)*(1+3*eta)/32;

                                                  2
      N[11] := (xi, eta) -> 9/32 (1 - xi) (1 - eta ) (1 + 3 eta)

> plot3d(N[11],-1..1,-1..1,grid=[15,15],axes=boxed,scaling=constrained,
> style=patch);

> 
> 
