> 
> N[2]:=-(1/4)*(1-eta)*(1-zeta)*(1+eta+zeta):
> N[3]:=-(1/4)*(1+eta)*(1-zeta)*(1-eta+zeta):
> N[6]:=-(1/4)*(1-eta)*(1+zeta)*(1+eta-zeta):
> N[7]:=-(1/4)*(1+eta)*(1+zeta)*(1-eta-zeta):
> N[10]:=(1/2)*(1-eta^2)*(1-zeta):
> N[18]:=(1-eta^2)*(1+zeta)/2:
> N[14]:=(1-zeta^2)*(1-eta)/2:
> N[15]:=(1-zeta^2)*(1+eta)/2:
> x(eta,zeta):=(N[10]+N[18]+N[14]+N[15])/2:
> x(eta,zeta):=simplify(%):
> y(eta,zeta):=-N[2]+N[3]-N[6]+N[7]-N[14]+N[15]:
> y(eta,zeta):=simplify(%):
> z(eta,zeta):=-N[2]-N[3]+N[6]+N[7]-N[10]+N[18]:
> z(eta,zeta):=simplify(%):
> plot1:=plot3d([x(eta,zeta)
> /infinity,y(eta,zeta),z(eta,zeta)],eta=-1..1,zeta=-1..1,axes=normal,co
> lor=black,orientation=[-60,80],style=wireframe):
> plot2:=plot3d([x(eta,zeta),y(eta,zeta),z(eta,zeta)],eta=-1..1,zeta=-1.
> .1,axes=normal,orientation=[-60,80],scaling=constrained,style=patchcon
> tour,shading=zgrayscale,tickmarks=[3,3,3]):
> plots[display]({plot1,plot2});

