> N[3]:=(xi,eta)->(1+xi)*(1+eta)/4;

             N[3] := (xi, eta) -> 1/4 (1 + xi) (1 + eta)

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

> 
> 
