BUILD & FIT - ELLIPSE

An ellipse can be defined symbolically by parameters a and b or by location of two foci and a point. What are the relations between these representations? In the left panel you can define a blue ellipse by varying the values of the a and b sliders. In the right panel you define the green ellipse by adjusting the location of the foci and a point (the BLACK dot) on the green ellipse. Now try to vary the green ellipse to match the blue one. Alternatively, start by defining a green ellipse in right panel, and see if you can adjust the a and b parameters in the left panel so that the blue ellipse matches the green one. What questions could/would you pose to your students based on this applet ?