 CALCULUS Understanding Its Concepts and Methods

A quadric surface is the set of all points (x,y,z)  that satisfy an equation of the form

Ax2 + By2 + Cz2 + Dxy + Exz + Fyz  + Gx + Hy + IzJ = 0

In order to sketch the graph of a quadric surface (or any surface), it is useful to look at the curves that intersect the surface with planes parallel to the axes of the surface. These curves are called traces (or cross-sections) of the surface.

The following equations and plots are in standard form and symmetric about the z-axis. Thus the traces are the intersections with the xy-planes, xz-planes, and yz-planes

A quadric surface with equation is an ellipsoid. Its traces are ellipses.

Quadric surfaces with equation are hyperbolic paraboloids. The traces are parabolas and hyperbolas.

Quadric surfaces with equation are elliptic paraboloids. The traces are parabolas and ellipses.

Quadric surfaces with equations are hyperboloids of one sheet. The traces in the xz-planes and yz-planes are hyperbolas, and the trace in any horizontal plane is an ellipse.

Quadric surfaces with equations are hyperboloids of two sheets. The traces in the xz-planes and yz-planes are hyperbolas, and the trace in any horizontal plane is an ellipse or misses the surface completely.

Quadric surfaces of the form are elliptic cones. The traces in the xz-planes and yz-planes are an intersecting pair of straight lines, and the trace in any horizontal plane is an ellipse. Copyright © 2006 Darel Hardy, Fred Richman, Carol Walker, Robert Wisner. All rights reserved. Except upon the express prior permission in writing, from the authors, no part of this work may be reproduced, transcribed, stored electronically, or transmitted in any form by any method.