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In geometry, a 120-gon is a polygon with 120 sides. The sum of any 120-gon's interior angles is 21240 degrees. Alternative names include dodecacontagon and hecatonicosagon.〔Norman Johnson, Geometries and Transformations (2015), Chapter 11, section 11.5 Spherical Coxeter groups, 11.5.5 ''full polychoric groups''〕 ==Regular 120-gon properties== A ''regular 120-gon'' is represented by Schläfli symbol and also can be constructed as a truncated hexacontagon, t, or a twice-truncated triacontagon, tt, or a thrice-truncated pentadecagon, ttt. One interior angle in a regular 120-gon is 177°, meaning that one exterior angle would be 3°. The area of a regular 120-gon is (with ) : and its inradius is : The circumradius of a regular 120-gon is : This means that the trigonometric functions of π/120 can be expressed in radicals. 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「120-gon」の詳細全文を読む スポンサード リンク
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