1概述三角形是平面图形中最简单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。因此,三角形的认识是学习平面图形知识的起点,为学习平面几何、立体几何打下基础。本节课是在学生已经学习了线段、角和直观认识了三角形的基础上进行教学的,所以,本节课是三角形认识的第二阶段。 1 Overview Triangles are the simplest and most basic polygons in a plan. All polygons can be divided into several triangles, and triangles can be used to derive related properties. Therefore, the understanding of the triangle is the starting point for learning the knowledge of plane graphics, laying the foundation for learning plane geometry and three-dimensional geometry. This lesson is based on students’ learning of line segments, corners, and intuitive triangles. Therefore, this lesson is the second phase of triangulation.