Linked from

The 12 pages that link to Focus (geometry), each with the reason it gives.

• Kepler's laws of planetary motionRelated: The Sun occupies one focus in the first law, not the ellipse's center.

• Conic sectionRelated: Foci characterize ellipses and hyperbolas and help define parabolas.

• Orbital eccentricityRelated: A central gravitating body lies at one focus of an ideal elliptical orbit.

• EllipseBroader topic: The two fixed points in the ellipse’s constant-distance-sum definition.

• ParabolaRelated: Every point on a parabola is as far from this point as from the directrix.

• Semimajor axisRelated: An ellipse’s foci lie on its major axis, whose half-length is the semimajor axis.

• Apollonius of PergaRelated: Later focal descriptions offer another way to characterize curves Apollonius studied.

• HyperbolaRelated: The two fixed points in the distance-difference definition are the hyperbola’s foci.

• Parabolic reflectorRelated: Rays parallel to the reflector’s axis meet at this point after reflection.

• True anomalyRelated: The orbiting primary lies at a focus, where true anomaly is measured.

• Kepler's first lawBroader topic: The Sun occupies one of the ellipse’s defining points.

• Marden's theoremBroader topic: The theorem locates the derivative zeros as the two foci of the inellipse.