[This question is probably aimed at Clark Kimberling.] I liked the little table at the beginning of this paper about which triangle thingy's generalized to 3-space and n-space. Is there a more encyclopedic version of this table, together with all the proofs? One of the most common questions by (insightful) high school geometry students is "what happens to this thingy in 3-space?". Also, the computation of such objects in higher spaces becomes more & more involved (as the computer graphics community knows all too well). Hopefully, such an encyclopedia would include some of these computational formulae. It would be nice to know where to point. At 09:14 PM 11/2/2011, Fred lunnon wrote:
See http://www.geometrie.tuwien.ac.at/havlicek/pub/hoehen.pdf Hans Havlicek, Gunter Weià "Altitudes of a Tetrahedron and Traceless Quadratic Forms" Tech. Univ. Vienna (no date?)