the quadratrix being traced out

> p := t -> [(1-t)/tan(Pi/2*(1-t)),(1-t)];

> quad := t -> plot([p(tau)[1],p(tau)[2],tau=0..t],color=yellow,thickness=3);

> frame3 := t -> plots[display]([sqr,seg1(t),seg2(t),quad(t)]);

> plots[display]([seq(frame3(i/40),i=0..40)],scaling=constrained,insequence=true);