> with(plots):with(plottools):

> x:=cos(t):y:=sin(t):

> k:=1/sqrt(2):

> u:=x*k:

> z:=(1-s)*2+s*u:

> a1:=plot3d([x,y,z],t=-Pi/3..Pi/3,s=0..1,scaling=constrained,grid=[20,5]):

> a2:=rotate(a1,0,0,2*Pi/3):

> a3:=rotate(a1,0,0,4*Pi/3):

> a:=display(a1,a2,a3):

> b1:=reflect(a,[[0,0,0],[1,0,k],[1,1,k]]):

> b2:=rotate(b1,0,0,2*Pi/3):

> b3:=rotate(b1,0,0,4*Pi/3):

> h:=display(a,b1,b2,b3):

> h;

> vrml(h,"C:/My Documents/trfa/wrl/11-14.wrl",background_color=white);

>