Dandelin Sphere Action!
- Tim Brzezinski
In the applet below, both spheres you see are tangent to the cone and are also tangent to the plane. These spheres are called Dandelin Spheres (in honor of Belgian mathematician Germinal Pierre Dandelin). The point at which each sphere is tangent to the plane is shown in blue. The cross section of the plane and cone is shown. What does this particular cross section look like? How does the action displayed (by sliding the slider) help illustrate this? Feel free to move any of the LARGE POINTS anywhere you like! Yet for this case, make sure that you see BOTH spheres at all times. What would need to happen in order for the conic section to change into another particular conic section? Explain. To explore in Augmented Reality, see the directions below this applet.
TO EXPLORE IN AUGMENTED REALITY:
1) Open up GeoGebra 3D app on your device. 2) Go to MENU (upper left corner). Go to OPEN. Under Search, type vfGNeMqJ Find the slider named w and slide it slowly.