Construct the concentric and coaxial ellipses
of constant area:

>

> restart;

> x:=tan(k*Pi/240)*cos(t):

> y:=cot(k*Pi/240)*sin(t):

> m:=[x,y,t=0..2*Pi]:

> plot([m$k=40..80],color=blue,scaling=constrained,axes=none);

>