Construct the family of ellipses

as t ranges in [0,1].

>

> restart;

> x:=(1-a)*cos(t):

> y:=a*sin(t):

> a:=k/20:

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

> plot([m$k=0..20],color=yellow,scaling=constrained,axes=none);

>