|
In geometry, an enneagram is a nine-pointed plane figure. It is sometimes called a nonagram. The name enneagram combines the numeral prefix, ''ennea-'', with the Greek suffix ''-gram''. The ''-gram'' suffix derives from ''γραμμῆς'' (''grammēs'') meaning a line.〔(γραμμή ), Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus〕 ==Regular enneagram== A ''regular enneagram'' (a nine-sided star polygon) is constructed using the same points as the regular enneagon but connected in fixed steps. It has two forms, represented by a Schläfli symbol as and , connecting every second and every fourth points respectively. There is also a ''star figure'', or 3, made from the regular enneagon points but connected as a compound of three equilateral triangles.〔Grünbaum, B. and G.C. Shephard; ''Tilings and Patterns'', New York: W. H. Freeman & Co., (1987), ISBN 0-7167-1193-1.〕〔Grünbaum, B.; Polyhedra with Hollow Faces, ''Proc of NATO-ASI Conference on Polytopes ... etc. (Toronto 1993)'', ed T. Bisztriczky et al., Kluwer Academic (1994) pp. 43-70.〕 (If the triangles are alternately interlaced, this results in a Brunnian link.) This star figure is sometimes known as the ''star of Goliath'', after or 2, the star of David.〔Weisstein, Eric W. "Nonagram". From ''MathWorld'' – A Wolfram Web Resource. http://mathworld.wolfram.com/Nonagram.html〕 This geometrical figure should not be confused with the logic puzzles called nonograms. or 3 |120px |} 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「Enneagram (geometry)」の詳細全文を読む スポンサード リンク
|
