directrix
Americannoun
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directrixes,
plural
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directrices
plural
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Geometry. a fixed line used in the description of a curve or surface.
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Archaic. a directress.
noun
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geometry a fixed reference line, situated on the convex side of a conic section, that is used when defining or calculating its eccentricity
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a directress
Gender
See -trix.
Other Word Forms
Noun Inflected Forms
Etymology
Origin of directrix
From New Latin, dating back to 1615–25; see origin at direct, -trix
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
A parabola is the set of points in the plane that lie equidistant from a fixed point, the focus, and a fixed line, the directrix.
From Textbooks ● Dec. 21, 2021
Hyperbola with and directrix units to the left of the pole.
From Textbooks ● Dec. 21, 2021
Hyperbola with and directrix units to the right of the pole.
From Textbooks ● Dec. 21, 2021
Find a polar equation of the conic with focus at the origin, eccentricity of and directrix:
From Textbooks ● Sep. 23, 2020
The triangles AA1A2 and BB1B2 formed by drawing perpendiculars from A and B to the directrix are also similar, so that AA1 : AA2 = = BB1 : BB2.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various
Figure 7.54 The three conic sections with their foci and directrices.
From Textbooks ● Mar. 30, 2016
Figure 1.54 The three conic sections with their foci and directrices.
From Textbooks ● Mar. 30, 2016
The ellipse and the hyperbola have two foci and two directrices.
From An Elementary Course in Synthetic Projective Geometry by Derrick Norman Lehmer
In the ellipse, which lies between the directrices, d1 + d2 is constant, therefore also r1 + r2.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various
The surface is thus generated by a variable hyperbola moving parallel to itself along the parabolas as directrices.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various
The ellipse and hyperbola have each two foci, and two corresponding directrixes, and the parabola has one focus and one directrix.
From The Gutenberg Webster's Unabridged Dictionary Section F, G and H by Project Gutenberg
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
