I made a circle with the center of the circle being the foci. The other point that is on the circle is the other foci. I then put another point on the circle and put a line from that point to the first foci. Then I connected the point from the circle to the second foci with a line segment. I then made the midpoint of the line segment and made a line perpendicular to the segment. Finally i traced the lines that intersect and turned on the animation.