usage note for directrix
Words nearby directrix
How to use directrix in a sentence
The surface formed by revolving the catenary about its directrix is named the alysseide.
Since the tension is measured by the height above the directrix these two catenaries have the same directrix.
The only surface of revolution having this property is the catenoid formed by the revolution of a catenary about its directrix.
Hence T, the point of intersection of Pp and Qq, must be the centre of similitude and must be on the common directrix.
If the directrix, focus and eccentricity be given, we may employ the general method for constructing a conic.