A quadric cone

   This figure shows a finite portion of a quadric cone. The quadric cone is the simplest quadric ruled surface, i.e., it is a surface of degree 2 that contains infinitely many lines. In fact, the vertex of the cone is at the origin, and every line that connects the origin to a point of the surface lies on the cone.
   In this version, cross sections perpendicular to the axis of the cone are circles, and the equation has the following form:
z² = a²(x² + y²),

where  a  is a nonzero real number. This figure was drawn with the value  a = 2.
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I made the figure on this page by substituting my own data in a Geometry Center webpage.

Prof. Joel Roberts
School of Mathematics
University of Minnesota
Minneapolis, MN 55455

Office: 351 Vincent Hall
Phone: (612) 625-1076
Dept. FAX: (612) 626-2017
e-mail: roberts@math.umn.edu