# An almost-theorem in a regular 10-gon

- Author:
- Zoltán Kovács

## Did you know?

A regular 10-gon that has side length 55, has two parallel diagonals with length 144 and 178.

## This is however not exactly true.

Just almost. 55 and 144 are Fibonacci numbers and therefore their ratio is very close to the golden ratio. Also, 178=144+34, a sum of two Fibonacci numbers (or one Fibonacci number twice, namely, 89+89). For these reasons the diagonals are very close to integers if the side is a Fibonacci number.