Construct twenty spheres of the same size each touching three others.

> restart:

> p:=2*Pi/5:

> phi:=(sqrt(5)+1)/2:

> with(plots):

Warning, the name changecoords has been redefined

> r:=2*sin(p/2):

> a1:=sphere([2*cos(p),2*sin(p),phi+1],r,color=red):

> a2:=sphere([2*cos(2*p),2*sin(2*p),phi+1],r,color=green):

> a3:=sphere([2*cos(3*p),2*sin(3*p),phi+1],r,color=blue):

> a4:=sphere([2*cos(4*p),2*sin(4*p),phi+1],r,color=gray):

> a5:=sphere([2*cos(5*p),2*sin(5*p),phi+1],r,color=yellow):

> b1:=sphere([2*phi*cos(p),2*phi*sin(p),phi-1],r,color=cyan):

> b2:=sphere([2*phi*cos(2*p),2*phi*sin(2*p),phi-1],r,color=coral):

> b3:=sphere([2*phi*cos(3*p),2*phi*sin(3*p),phi-1],r,color=brown):

> b4:=sphere([2*phi*cos(4*p),2*phi*sin(4*p),phi-1],r,color=pink):

> b5:=sphere([2*phi*cos(5*p),2*phi*sin(5*p),phi-1],r,color=magenta):

> c1:=sphere(-[2*cos(5*p),2*sin(5*p),phi+1],r,color=orange):

> c2:=sphere(-[2*cos(4*p),2*sin(4*p),phi+1],r,color=violet):

> c3:=sphere(-[2*cos(3*p),2*sin(3*p),phi+1],r,color=COLOR(RGB,3,1,1)):

> c4:=sphere(-[2*cos(2*p),2*sin(2*p),phi+1],r,color=COLOR(RGB,1,2,1)):

> c5:=sphere(-[2*cos(p),2*sin(p),phi+1],r,color=COLOR(RGB,1,0.9,2)):

> d1:=sphere(-[2*phi*cos(5*p),2*phi*sin(5*p),phi-1],r,color=COLOR(RGB,2,0.8,1)):

> d2:=sphere(-[2*phi*cos(4*p),2*phi*sin(4*p),phi-1],r,color=COLOR(RGB,2,0.5,1)):

> d3:=sphere(-[2*phi*cos(3*p),2*phi*sin(3*p),phi-1],r,color=COLOR(RGB,0.5,3,2)):

> d4:=sphere(-[2*phi*cos(2*p),2*phi*sin(2*p),phi-1],r,color=COLOR(RGB,1,1,0.8)):

> d5:=sphere(-[2*phi*cos(p),2*phi*sin(p),phi-1],r,color=COLOR(RGB,0.7,1,0.8)):

> e:=display(a1,a2,a3,a4,a5,b1,b2,b3,b4,b5,c1,c2,c3,c4,c5,d1,d2,d3,d4,d5,scaling=constrained):

> e;

>

> vrml(e,"c:/042/9/9-12.wrl",background_color=white);

>