Construct the envelope of the light rays emitted from a radiant point source at infinity after reflection by the semi-circle.

> restart;

> m:=[[-3,sin(t)],[cos(t),sin(t)],[cos(t)-cos(2*t),sin(t)-sin(2*t)]];

> t:=k*Pi/50-Pi/2;

> plot([m$k=0..50],axes=none,scaling=constrained,color=red);

>