Definition of directrix in English:

directrix

Line breaks: dir|ec¦trix
Pronunciation: /dɪˈrɛktrɪks
 
, dʌɪ-/

noun (plural directrices /-trɪsiːz/)

Geometry
  • A fixed line used in describing a curve or surface.
    More example sentences
    • In the following, the feet of perpendiculars dropped from points A, B, etc. on the parabola to the directrix will be denoted A ’, B ’, etc.
    • The focus and directrix of a hyperbola were considered by Pappus.
    • The directrix is used in the construction, which follows, mutatis mutandis, the same course as the above construction in the case of the ellipse.

Origin

early 18th century: from medieval Latin, literally 'directress', based on Latin dirigere 'to guide'.

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