411 REFERENCE · Wikibooks
Geometry/Ellipses
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Ellipses
Ellipses are sometimes called ovals. Ellipses contain two foci. The sum of the distance from a point on the ellipse to one focus and that same point to the other focus is constant
Image:Ellipse.jpg