Triangle Centers in the 2D, 3D, Spherical and Hyperbolic

At Wolfram Demonstrations, I perused the greater triangle center material that we had, including a new one.

Fate of the Euler Line and the Nine-Point Circle on the Sphere
by Paolo Maraner

Non-Euclidean Triangle Continuum
by Robert A. Russell

Tetrahedron Centers
by Ed Pegg Jr

Also items like Triangle Calculator and Spherical Triangle Solutions, along with many recent submissions by Izidor Hafner. After writing the third demo above, I was surprised to rediscover the second, and astounded by the discussions in the first. In 2D euclidean space, these points in a triangle are known as Kimberling Centers. In 3D euclidean space, spherical geometry and hyperbolic geometry; many of these same points exist, but exact areal coordinates for them are not yet known. It seems like they should be findable, though, with this much interplay.

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My paper at [1608.08190] Non-Euclidean Triangle Centers has non-Euclidean coordinates for many triangle centers.

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That’s very nice. Thank you for bringing it to my attention.