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Directrix of a Parabola

A line perpendicular to the axis of symmetry used in the definition of a parabola. A parabola is defined as follows: For a given point, called the focus, and a given line not through the focus, called the directrix, a parabola is the locus of points such that the distance to the focus equals the distance to the directrix.

 

 

Example:  

This is a graph of the parabola with all its major features labeled: axis of symmetry, focus, vertex, and directrix.

 

See also

Directrices of an ellipse, directrices of a hyperbola

 


  this page updated 15-jul-23
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
Copyright © 2000 by Bruce Simmons
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