Invisible Tetrahedron
← Invisible Tetrahedron (2) | Invisible Tetrahedron →
Index Entry
Invisible Tetrahedron:
"Descartes discovered the 720° but he didn't call it the tetrahedron. cf. Letter from Coxeter, 30 Oct. '70. The tetrahedron can be turned inside out; it can become invisible. There is an internal invisible tetrahedron of concave angles, 720° or less."
Citations
- RBF to EJA, Blackstone Hotel, Chicago, 31 May 1971
