directrix

American  

[dih-rek-triks, dahy-] / dɪˈrɛk trɪks, daɪ- /

noun

plural

directrixes, directrices

1. Geometry. a fixed line used in the description of a curve or surface.

2. Archaic. a directress.

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directrix British  

/ daɪ-, dɪˈrɛktrɪks /

noun

1. geometry a fixed reference line, situated on the convex side of a conic section, that is used when defining or calculating its eccentricity

2. a directress

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directrix Scientific  

/ dĭ-rĕk′trĭks /

1. A straight line used in generating a curve such as a parabola.

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Gender

See -trix.

Etymology

Origin of directrix

From New Latin, dating back to 1615–25; direct, -trix

Example Sentences

Ellipse with and directrix unit above the pole.

From Textbooks • Dec. 21, 2021

Parabola with and directrix units below the pole.

From Textbooks • Dec. 21, 2021

Ellipse with and directrix units to the right of the pole.

From Textbooks • Sep. 23, 2020

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

Hence the tangents at A and B to the upper catenary must intersect above the directrix, and the tangents at A and B to the lower catenary must intersect below the directrix.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" by Various