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__NOTOC__ The dangerous bend or caution symbol ☡ () was created by the Nicolas Bourbaki group of mathematicians and appears in the margins of mathematics books written by the group. It resembles a road sign that indicates a "dangerous bend" in the road ahead, and is used to mark passages tricky on a first reading or with an especially difficult argument.〔Steven G. Krantz (2011), ''(The Proof Is in the Pudding: The Changing Nature of Mathematical Proof )'', Springer, ISBN 0-387-48908-8, p. 92.〕 Others have used variations of the symbol in their textbooks, and computer scientist Donald Knuth introduced an American-style road-sign depiction in his Metafont and TeX systems, with a pair of adjacent signs indicating doubly dangerous passages.〔Donald Ervin Knuth (1984), ''(The TeXbook )'', Addison-Wesley, ISBN 0-201-13448-9.〕〔Donald Ervin Knuth (1986), ''(The METAFONTbook )'', Addison-Wesley, ISBN 0-201-13445-4.〕〔George J. Tourlakis (2003), ''(Lectures in Logic and Set Theory, Volume 2: Set Theory )'', Cambridge University Press, ISBN 0-521-75374-0, p. xiv.〕〔Gerard P. Michon (2012), ''(Dangerous Bend Symbol, doubled and tripled )'', Numericana〕 ==Typography== In the LaTeX typesetting system, Knuth's dangerous bend symbol can be produced by first loading the font manfnt (a font with extra symbols used in Knuth's TeX manual) with :\usepackage and then typing :\dbend There are several variations given by \lhdbend, \reversedvideodbend, \textdbend, \textlhdbend, and \textreversedvideodbend. 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「Bourbaki dangerous bend symbol」の詳細全文を読む スポンサード リンク
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