Adjust foci to see various ellipses Set face left focus? to 1 then try 0 for right focus
Within circle, draws perpendicular lines to segments connecting the point within to the circle's points. The resulting perpendicular lines together make an ellipse "envelope." Foci are x coordinate of each focus, one + and one - Pick one of the points within the circle. Draw perpendicular lines to segments connecting this point with the points of the circle. To do this in Scratch, I have the circling sprite stamps a line facing the left or right focus (either left or right focus will create the same ellipse).
