# Ellipse/Related Articles

From Citizendium, the Citizens' Compendium

< Ellipse

*See also changes related to Ellipse, or pages that link to Ellipse or to this page or whose text contains "Ellipse".*

## Parent topics

- Conic [r]: A curve obtained as the intersection of a plane with a circular cone; also called second order curve because of its algebraic representation.
^{[e]} - Second order curve [r]: A planar curve defined by a quadratic equation:
*ax*^{2}+*bxy*+*cy*^{2}+*dx*+*ey*+*f*= 0 in the affine plane, or in the projective plane; also called a conic because of its geometrical generation.^{[e]}

## Subtopics

- Parabola [r]: The planar curve formed by the points that lie as far from a given line (the directrix) as from a given point (the focus).
^{[e]} - Hyperbola [r]: Planar curve formed by the points for which the difference of the distances to two given points is a given number.
^{[e]}

- Kepler's first law [r]: Planets move on paths that are ellipses which have the sun as a focus.
^{[e]}