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In mathematics, in geometry, geometrography is the study of geometrical constructions. The concepts and methods of geometrography were first expounded by Émile Lemoine (1840–1912), a French civil engineer and a mathematician, in a meeting of the French Association for the Advancement of the Sciences held at Oran in 1888. 〔 Lemoine later expanded his ideas in another memoir read at the Pau meeting of the same Association held in 1892. It is well known in elementary geometry that certain geometrical constructions are simpler than certain others. But in many case it turns out that the apparent simplicity of a construction does not consist in the practical execution of the construction, but in the brevity of the statement of what has to be done. Can then any objective criterion be laid down by which an estimate may be formed of the relative simplicity of several different constructions for attaining the same end? Lemoine developed the ideas of geometrography to answer this question.〔 ==Basic ideas== In developing the ideas of geometrography, Lemoine restricted himself to Euclidean constructions using rulers and compasses alone. According to the analysis of Lemoine, all such constructions can be executed, as a sequence of operations selected form a fixed set of five elementary operations. The five elementary operations identified by Lemoine are the following: Elementary operations in a geometrical construction In a geometrical construction the fact that an operation X is to be done ''n'' times is denoted by the expression ''n''X. The operation of placing a ruler in coincidence with two points is indicated by 2R1. The operation of putting one point of the compasses on a determinate point and the other point of the compasses on another determinate point is 2C1. Every geometrical construction can be represented by an expression of the following form :''l''1R1 + ''l''2R2 + ''m''1C1 + ''m''2C2 + ''m''3C3. Here the coefficients ''l''1, etc. denote the number of times any particular operation is performed. 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「Geometrography」の詳細全文を読む スポンサード リンク
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