# Directrix

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## directrix

[də′rek·triks] (mathematics)

A fixed line used in one method of defining a conic; the distance from this line divided by the distance from a fixed point (called the focus) is the same for all points on the conic.

A curve through which a line generating a given ruled surface always passes.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from

*The Great Soviet Encyclopedia*(1979). It might be outdated or ideologically biased.## Directrix

in artillery, a specially equipped sector of an artillery range or troop training center: targets are installed, artillery fire positions and observation points are rigged out, and so on. These sectors are designed for artillery fire (artillery directrix), tank fire (tank directrix), antiaircraft artillery fire against ground targets (antiaircraft artillery directrix), and other weapons.

## Directrix

(of a ruled surface), a curve along which a point on a line moves such that the ruled surface is circumscribed by the motion of the line. Any curve intersecting all the generatrices may be taken as the directrix.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.