9 - polytope is what you call for a 9 sided polygon.
9 - polytope is what you call for a 9 sided polygon.
what do you call a 9 sided polygon?
9 - polytope
nonagon









































in geometry, a nonagon () or enneagon () is a nine-sided polygon or 9-gon.









































the name "nonagon" is a prefix hybrid formation, from latin ("nonus", "ninth" + "gonon"), used equivalently, attested already in the 16th century in french "nonogone" and in english from the 17th century. the name "enneagon" comes from greek "enneagonon" (εννεα, "nine" + γωνον (from γωνία = "corner")), and is arguably more correct, though less common than "nonagon".









































section::::regular nonagon.
nonagon
in ancient china, values for included 3.1547 (around 1 ad), (100 ad, approximately 3.1623), and (3rd century, approximately 3.1556). around 265 ad, the wei kingdom mathematician liu hui created a polygon-based iterative algorithm and used it with a 3,072-sided polygon to obtain a value of of 3.1416. liu later invented a faster method of calculating and obtained a value of 3.14 with a 96-sided polygon, by taking advantage of the fact that the differences in area of successive polygons form a geometric series with a factor of 4. the chinese mathematician zu chongzhi, around 480 ad, calculated that and suggested the approximations = 3.14159292035... and = 3.142857142857..., which he termed the "milü" ("close ratio") and "yuelü" ("approximate ratio"), respectively, using liu hui's algorithm applied to a 12,288-sided polygon. with a correct value for its seven first decimal digits, this value of remained the most accurate approximation of available for the next 800 years.
pi