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笔者在使用北师大版初中数学教科书过程中,发现九年级数学(上)中三角形中位线定理的证明在教材编排顺序和定理证明的难易程度上存在不足,有待改进.一、三角形中位线在教材中的编排顺序不合理三角形中位线定理这一内容安排在九年级(上)第三章“证明(三)”第一节(平行四边形)的第三个课时.这个定理在解决三角形相似和有关三角形边长计算过程中使用方便、快捷.这个定理应该编排在八年级(下)的第四章第6节(探索三角形相似的条件)后
During the process of using junior high school mathematics textbooks of Beijing Normal University, the author finds that the proof of the bit-line theorem of the mid-point triangle in mathematics (middle) of ninth grade is deficient in the difficulty of the order and theorem proving of textbooks and needs to be improved. The bit line arrangement in the textbook is not in the proper order The bit line theorem in the triangle is arranged in the third lesson of the third chapter of the ninth grade (above) (parallelogram) The theorem is easy and quick to use in solving the triangle similarity and the calculation of the triangle side length.This theorem should be arranged in the eighth grade (below), Chapter 4, Section 6 (explore the similar conditions of the triangle)