Fun Time

To see the angle relationships in various polygons:

https://www.mathsisfun.com/geometry/polygons-interactive.html

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Isaac Newton was born 100 years after Viète. His approximation formula for
pi is additive.

It starts by answering the question: what is  arcsin(.5). It is pi/6, the zero
iteration of the formula. Subsequent iterations add small amounts, which
multiplied by 6, yield pi.

http://pi314.net/fr/newton.php

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source: Wikipedia