Informally, right-angled hyperbolic hexagon is a hyperbolic triangle with vertices outside infinity. I think there should be a Gram matrix for it, and **what does it looks like?**
(The Gram matrix here defines the existence of a simplex)


Also, for hyperbolic truncated tetrahedron or hyperbolic truncated n-simplex what’s the form of its Gram matrix?


Thanks.



What’s the form of Gram matrix for right-angled hexagon
Why do you mean by "what is the form"? And which Gram matrix? (there are two). But if you mean the usual Gram matrix, then the $ij$ element is $-\cosh d(s\_i, s\_j),$ where $s\_i$ is the $2i$-th side of the hexagon.


