e/Proofs involving the ellipse

Information
has gloss	eng: The derivation of the cartesian form for an ellipse is simple and instructive. One simple definition of the ellipse is the "locus of all points of the plane whose distances to two fixed points(called the foci) add to the same constant". See ellipse for other definitions.
lexicalization	eng: Proofs involving the ellipse
instance of	(noun) (geometry) a curve generated by the intersection of a plane and a circular cone conic, conic section

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media:img	Ellipse derivation 1.jpg