Copia de Dandelin's theorem in stereo

* Move points A and B to change section of the cone[br]* Spheres are tangent to the plane and to the cone[br]* Move point P on the conic[br]* When the conic is an ellipse, why is MP+PH constant ?
– Lorenzo Cubeles Blasco, Mathieu Blossier

Information: Copia de Dandelin's theorem in stereo