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:
Ellipse with and directrix unit above the pole.
From Textbooks ● Dec. 21, 2021
Hyperbola with and directrix units to the right of the pole.
From Textbooks ● Dec. 21, 2021
The directrix will be parallel to the polar axis.
From Textbooks ● Dec. 21, 2021
For the following exercises, rewrite the given equation in standard form, and then determine the vertex focus and directrix of the parabola.
From Textbooks ● Sep. 23, 2020
The centre of a circle is its focus, and its directrix has gone to infinity, having no special direction.
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
In the hyperbola on the other hand d1 − d2 is constant, equal to the distance between the directrices, therefore in this case r1 − r2 is constant.
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
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 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
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