Japanese triangulation theorem

Let a convex cyclic polygon be triangulated in any manner, and draw the incircle to each triangle so constructed. Then the sum of the inradii is a constant independent of the triangulation chosen. This theorem can be proved using Carnot's theorem. In the above figures, for example, the inradii of the left triangulation are 0.142479, 0.156972, 0.232307, 0.498525, and the inradii of the right triangulation are 0.157243, 0.206644, 0.312037, 0.354359, giving a sum of 1.03028 in each case. According to an ancient custom of Japanese mathematicians, this theorem was a Sangaku problem inscribed on tablets hung in a Japanese temple to honor the gods and the author in 1800.

Carnot's theorem | cyclic polygon | incircle | inradius | sangaku problem | triangulation