This class is intended to test the computation of prinicpal curvatures and
radii for ellipsoids, based on the first and second fundamental forms.
For computing the fundamental forms of ellipsoid, see
http://mathworld.wolfram.com/Ellipsoid.html.
For details on how to use these to compute the principal directions and
radii, see Basics of the Differential Geometry of Surfaces, by Gallier,
http://www.cis.upenn.edu/~cis610/gma-v2-chap20.pdf, and Curvature of
ellipsoids and other surfaces, by W.F. Harris (2006).