This article surveys some of the more aesthetically appealing and useful formulas relating distances, areas, and angles in triangles and tetrahedra. For example, a somewhat neglected trigonometric identity involving only the cosines of a triangle is an instance of the famous Cayley cubic surface. While most of these formulas are well known, some novel identities also make an appearance. Heron’s...

It will be shown that according to theorems of K. Menger, every neuron grid if identified with a curve is able to preserve the adopted qualitative structure of a data space. Furthermore, if this identification is made, the neuron grid structure can always be mapped to a subset of a universal neuron grid which is constructable in three space dimensions. Conclusions will be drawn for established ...