Changes

[[File:lighterstill.jpg]][[File:Ellipse_mean.gif|right|frame]]

[[File:lighterstill.jpg]][[File:Sd_ellipse_sm.jpg|right|frame]]

 

==Etymology==

==Etymology==

Greek elleipsis

Greek elleipsis

*Date: circa [http://en.wikipedia.org/wiki/18th_Century 1753]

*Date: circa [http://en.wikipedia.org/wiki/18th_Century 1753]

==Definitions==

==Definitions==

*1 a : oval  

*1 a : oval  

:b : a closed plane curve generated by a point moving in such a way that the sums of its distances from two fixed points is a constant : a plane section of a right circular cone that is a closed curve

:b : a closed plane curve generated by a point moving in such a way that the sums of its distances from two fixed points is a constant : a plane section of a right circular cone that is a closed curve

==Description==

==Description==

In [[geometry]], an '''ellipse''' (from Greek ἔλλειψις elleipsis, a "falling short") is a [http://en.wikipedia.org/wiki/Plane_curve plane curve] that results from the intersection of a cone by a plane in a way that produces a closed curve. [[Circle]]s are special cases of ellipses, obtained when the cutting plane is perpendicular to the axis. An ellipse is also the locus of all points of the plane whose distances to two fixed points add to the same constant.

In [[geometry]], an '''ellipse''' (from Greek ἔλλειψις elleipsis, a "falling short") is a [http://en.wikipedia.org/wiki/Plane_curve plane curve] that results from the intersection of a cone by a plane in a way that produces a closed curve. [[Circle]]s are special cases of ellipses, obtained when the cutting plane is perpendicular to the axis. An ellipse is also the locus of all points of the plane whose distances to two fixed points add to the same constant.