Parametric equation [math]X(t)=[x(t),y(t)][/math] describes the circle.[br]When [i]t[/i] moves to infinity, x approaches 0 while[i] y[/i] approaches -1 (use L'Hospital's rule).

Animation of moving point[i] A[/i], where [math]X(t)[/math] generate it's trajectory with time [i]t[/i].