Wikipedia contributors. (2023, August 28). Octagon. In Wikipedia, The Free Encyclopedia. Retrieved October 31, 2023, from https://en.wikipedia.org/w/index.php?title=Octagon&oldid=1172616040
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/mathematics/shapes/octagon/sum-of-internal-angles/en.wikipedia.org.snippet-properties-1-1.md
Octagon (Wikipedia) In geometry, an octagon (from the Greek ὀκτάγωνον oktágōnon, “eight angles”) is an eight-sided polygon or 8-gon.