The surface which is the inverse of the Ellipsoid in the sense that it ``goes in'' where the Ellipsoid ``goes
out.'' It is given by the parametric equations

for and . The special case corresponds to the Hyperbolic Octahedron.

**References**

Nordstrand, T. ``Astroidal Ellipsoid.'' http://www.uib.no/people/nfytn/asttxt.htm.

© 1996-9

1999-05-25