Recall the major vertices of an ellipse are the end points of the major axis.[br][br]The distance from the center to the horizontal vertices is a.[br]The vertical distance from the center to the vertical vertices is b.[br][br]The underlying "force" of an ellipse are the foci.[br]They are what tie the major and minor vertices together.[br][br]Play around with the ellipse to see the foci interact with the ellipse. [br]If you make a=4, and b=5 or vice versa pay careful attention to the foci points!