Focus

A point related to the construction and properties of conic sections. Hyperbolas and noncircular ellipses have two distinct foci and two associated conic section directrices, each directrix being perpendicular to the line joining the two foci (Eves 1965, p. 275).

See also

Conic Section Directrix, Eccentricity, Ellipse, Ellipsoid, Focal Parameter, Hyperbola, Hyperboloid, Parabola, Paraboloid, Reflection Property

Explore with Wolfram|Alpha

References

Coxeter, H. S. M. and Greitzer, S. L. Geometry Revisited. Washington, DC: Math. Assoc. Amer., pp. 141-144, 1967.Eves, H. "The Focus-Directrix Property." §6.8 in A Survey of Geometry, rev. ed. Boston, MA: Allyn & Bacon, pp. 272-275, 1965.

Referenced on Wolfram|Alpha

Focus

Cite this as:

Weisstein, Eric W. "Focus." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Focus.html

Subject classifications