Algebra: Ellipse *20 pts*

Ellipse comes from the Greek ελλιψη(elliyh), literally absence
Pythagoras and Apollonios contributed to the forming and equations of ellipse

Germinal Pierre Dandelin (April 12, 1794 - February 15, 1847) was a mathematician, soldier, and professor of engineering.
He is the eponym of the Dandelin spheres, of Dandelin's theorem in geometry, and of the Dandelin-Gräffe numerical method of solution of algebraic equations. He also published on the stereographic projection, algebra, and probability theory.

Dandelin’s theorem
In geometry, a nondegenerate conic section formed by a plane intersecting a cone has one or two Dandelin spheres characterized thus:
Each Dandelin sphere touches, but does not cross, both the plane and the cone.
Each conic section has one Dandelin sphere for each focus.
An ellipse has two Dandelin spheres, both touching the same nappe of the cone.
A hyperbola has two Dandelin spheres, touching opposite nappes of the cone.
A parabola has just one Dandelin sphere.


Apollonios，應該是Apollonius 吧
他有 一個Apollonius’ Derivation 和 ellipse有關
不過我少手上沒有資料


雖然資料來源是維基百科，但我有作出修改，並不是直接複製