Section 11.7 #jh1
> circ1:=[cos(t),sin(t),0];
> circ2:=[cos(t),0,sin(t)];
> circ3:=[0,cos(t),sin(t)];
>
tubeplot({circ1,circ2,circ3},t=0..2*Pi,radius=1/5,scaling=constrained,
axes=frame,labels=['x','y','z'],orientation=[22,75]);
>