>

> restart;

> with(plots):with(plottools):

Warning, the name changecoords has been redefined

> a1:=display(a,scaling=constrained):

> a2:=rotate(a1,2*Pi/3,[[1,1,1],[0,0,0]]):

> a3:=rotate(a1,4*Pi/3,[[1,1,1],[0,0,0]]):

> b1:=polygon([[1,1,-1],[1,0,-1],[0,1,-1]]):

> b2:=rotate(b1,2*Pi/3,[[1,1,1],[0,0,0]]):

> b3:=rotate(b1,4*Pi/3,[[1,1,1],[0,0,0]]):

> half1:=display(a1,a2,a3,b1,b2,b3):

> with(plottools):

> vrml(half1,"d:/87116/12081.wrl",background_color=white);

> half1;

> half2:=reflect(half1,[0,0,0]):

> hexagon:=polygon([[1,-1,0],[0,-1,1],[-1,0,1],[-1,1,0],[0,1,-1],[1,0,-1]],color=pink,thickness=1):

> c1:=display(half1,hexagon):

> with(plottools):

> vrml(c,"d:/87116/12082.wrl",background_color=white);

> c1;

> c:=display(half1,half2,hexagon):

> with(plottools):

> vrml(c,"d:/87116/12083.wrl",background_color=white);

> c;

>

> restart;

> z:=rho*cos(phi):

> r:=rho*sin(phi):

> x:=r*cos(theta):

> y:=r*sin(theta):

> rho:=2*cos(phi)*sin(phi)^2:

> c1:=plot3d([x,y,z],theta=0..2*Pi,phi=0..Pi/2,scaling=constrained,grid=[20,50]):

> with(plottools):

> vrml(c1,"d:/87116/12091.wrl",background_color=white);

> c1;

> c2:=plot3d([x,y,z],theta=0..Pi,phi=0..Pi/2,scaling=constrained,grid=[20,50]):

> with(plottools):

> vrml(c2,"d:/87116/12092.wrl",background_color=white);

> c2;

>

> restart;

> c1:=plot3d(4-sqrt(abs(x*y)),x=-2..2,y=-2..2,scaling=constrained):

> with(plottools):

> vrml(c1,"d:/87116/1210.wrl",background_color=white);

> c1;

> x:=r*cos(t):

> y:=r*sin(t):

> z:=4-sqrt(abs(x*y)):

> c2:=plot3d([x,y,z],r=0..2,t=0..2*Pi,scaling=constrained,grid=[20,101]):

> with(plottools):

> vrml(c2,"d:/87116/1211.wrl",background_color=white);

> c2;

>

> restart;

> x:=r*cos(t):

> y:=r*sin(t):

> c:=plot3d([x,y,x*y/(x^2+y^2)],r=0..1,t=0..2*Pi,scaling=constrained,grid=[20,50]):

> with(plottools):

> vrml(c,"d:/87116/1212.wrl",background_color=white);

> c;

>

> x:=r*cos(t)/sqrt(2):

> y:=r*sin(t):

> z:=5*x^2+5*y^2:

> with(plots):

Warning, the name changecoords has been redefined

> z:=6-7*x^2-y^2:

> b:=plot3d([x,y,z],r=0..1,t=0..2*Pi,scaling=constrained,color=red):

> c:=display(a,b):

> with(plottools):

> vrml(c,"d:/87116/1213.wrl",background_color=white);

> c;

>