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

> restart;

> m:=[[3*cos(t)-cos(3*t),3*sin(t)-sin(3*t)],[3*cos(t)+cos(3*t),3*sin(t)+sin(3*t)]]:

> t:=k*Pi/100:

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

>