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In geometry, an octacontagon (or ogdoëcontagon from Ancient Greek ὁγδοήκοντα, eighty〔(Greek Numbers and Numerals (Ancient and Modern) ) by Harry Foundalis〕) is an eighty-sided polygon or 80-gon.〔.〕〔(''The New Elements of Mathematics: Algebra and Geometry ) by Charles Sanders Peirce (1976), p.298〕 The sum of any octacontagon's interior angles is 14040 degrees. ==Regular octacontagon == A ''regular octacontagon'' is represented by Schläfli symbol and can also be constructed as a truncated tetracontagon, t, or a twice-truncated icosagon, tt, or a thrice-truncated decagon, ttt, or a four-fold-truncated pentagon, tttt. One interior angle in a regular octacontagon is 175.5°, meaning that one exterior angle would be 4.5°. The area of a regular octacontagon is (with ) : and its inradius is : The circumradius of a regular octacontagon is : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Octacontagon」の詳細全文を読む スポンサード リンク
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