# Four Visual Proofs of a Theorem about a Regular Nonagon

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This Demonstration shows four visual proofs that , where , , and are the lengths of a side, the shortest diagonal, and the longest diagonal, respectively, of a regular nonagon. The interior angle of the regular nonagon is , so that angle 451 equals .

Contributed by: Izidor Hafner (January 2016)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

Reference

[1] Š. Arslanagić, *Matematička čitanka 4*, Sarajevo, 2012, pp. 63–72.

## Permanent Citation

"Four Visual Proofs of a Theorem about a Regular Nonagon"

http://demonstrations.wolfram.com/FourVisualProofsOfATheoremAboutARegularNonagon/

Wolfram Demonstrations Project

Published: January 12 2016