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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Nonagon ： ウィキペディア英語版 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 somewhat less common than "nonagon". == Regular nonagon== A ''regular nonagon'' is represented by Schläfli symbol and has internal angles of 140°. The area of a regular nonagon of side length ''a'' is given by :$A\; =\; \backslash fraca^2\backslash cot\backslash frac=(9/2)ar\; =\; 9r^2\backslash tan(\backslash pi/9)$ :::$=\; (9/2)R^2\backslash sin(2\backslash pi/9)\backslash simeq6.18182\backslash ,a^2,$ where the radius ''r'' of the inscribed circle of the regular nonagon is :$r=(a/2)\backslash cot(\backslash pi/9)$ and where ''R'' is the radius of its circumscribed circle: :$R\; =\; \backslash sqrt=r\backslash sec(\backslash pi/9).$ 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「Nonagon」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.