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三角形在平面图形中是最简单的、也是最基本的多边形。一切多边形都可以分割成若干个三角形,并借助三角形来推导有关的性质。所以掌握三角形的特征是很重要的。这部分内容是在学生已经学习线段、角和直观认识了三角形的基础上进行教学的。教材先通过学生熟悉的具有三角形形状的物体,结合操作演示,抽象概括出三角形的定义,发现三角形的稳定性及其应用,然后根据一定的分类标准给三角形进行分类。
Triangles are the simplest and most basic polygons in a plan. All polygons can be divided into a number of triangles, and use the triangle to derive the nature of the. So to grasp the characteristics of the triangle is very important. This part is based on the students have learned the line, angle and intuitive understanding of the triangle based on teaching. Teaching materials first through the students familiar with the object of the shape of the triangle, combined with operational demonstration, abstracted out the definition of the triangle abstract, found the stability of the triangle and its application, and then classified according to certain classification criteria for the triangle.