19 Feb
2016
19 Feb
'16
7:09 p.m.
Reminder --- r_EX is negative! On 2/20/16, Fred Lunnon <fred.lunnon@gmail.com> wrote:
A neat identity relates inradius r_IN , ex-radius r_EX , altitude h , of a simplex with distinguished base and apex ---
*** 1/r_EX + 1/r_IN = 2/h ***
--- the altitude equals the harmonic mean of the radii !
I have not come across this elsewhere --- reference, anyone?
A fellow by name of Ilya Bogdanov on Math Overflow (carefully rinsing mouth with disinfectant) seems well versed in this stuff. There turn out to be a good few Ilya Bogdanovs in Russia ... does anybody have an email address for this one?
WFL