# Dynamic Geometry 1480: Japanese Theorem for Cyclic Polygon,
Sangaku, Triangulation, Non-intersecting Diagonals, Sum of Inradii, Invariant, Step-by-step Illustration

Let a cyclic polygon be triangulated in any manner by non-intersecting diagonals. Prove that the sum of the inradii of the triangles formed is a constant independent of the triangulation chosen
(invariant).

Reference:
Weisstein, Eric W. "Japanese
Theorem." From *MathWorld*--A
Wolfram Web Resource. https://mathworld.wolfram.com/JapaneseTheorem.html

## Static Diagram of Dynamic Geometry 1480

## Poster of Dynamic Geometry 1480 using iPad Apps

###
Classroom Resource:

Interactive step-by-step animation using GeoGebra

This step-by-step interactive illustration was created with
GeoGebra.

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