Wallis's conical edge



In geometry, Wallis's conical edge is a ruled surface given by the parametric equations
 * $$x=v\cos u,\quad y=v\sin u,\quad z=c\sqrt{a^2-b^2\cos^2u}$$

where $a$, $b$ and $c$ are constants.

Wallis's conical edge is also a kind of right conoid. It is named after the English mathematician John Wallis, who was one of the first to use Cartesian methods to study conic sections.