在几何“四边形”这一章中 ,主要内容是有关四边形、多边形的概念和性质 .要学好这些内容 ,关键是抓好两个转化 .一、将四边形 (多边形 )转化为三角形来研究利用对角线往往可以把多边形问题转化为三角形问题来解决 ,如四边形内角和定理的证明就是从四边形的一个顶点引一条对角 In the chapter of “geometry” of geometry, the main content is about the concept and nature of quadrilaterals and polygons. The key to studying these elements is to do a good job of two transformations. 1. Convert quadrilaterals (polygons) to triangles to study the use of diagonals. Lines can often be solved by transforming the polygon problem into a triangular problem. For example, the inner angle of a quadrilateral and the proof of the theorem is to lead a diagonal from a vertex of a quadrilateral.