Construct the envelope formed by a fix diameter of a circle rolling along a fixed circle of the same
size.

>

> restart;

> m:=[[2*cos(t)-cos(2*t),2*sin(t)-sin(2*t)],[2*cos(t)+cos(2*t),2*sin(t)+sin(2*t)]]:

> t:=k*Pi/100:

> plot([m$k=0..200],color=green,scaling=constrained,axes=none);

>