在众多数学思想和解题方法中,转化思想是最基础、最重要的方法之一,简单来说,就是把未知问题转化为已解决问题,把不熟悉、复杂的问题转化为熟悉、简单的问题下面笔者结合“多边形内角和与外角和公式”实际教学,就转化思想在多边形内外角和中的运用谈一谈自己的体会.问题1三角形内角和定理的证明方法1如图1-1,延长BC至点D,过点C作CE∥AB,根据平行线的性质,得∠A=∠ACE,∠B=∠ECD,从而把三角形的三个内角的和转化为一个平 Among many mathematical ideas and problem-solving methods, the idea of ​​transformation is one of the most basic and important methods. In simple terms, it transforms an unknown problem into a solved problem and an unfamiliar and complicated one into a familiar and simple Problem below the author combined with “polygon interior angle and exterior angle and formula ” actual teaching, on the conversion of ideas in the polygon inside and outside the corner and talk about his experience. Question 1 Triangle interior angle and theorem proving method 1 As shown in Figure 1- 1. Extend BC to point D and point C for CE∥AB. According to the properties of parallel lines, get ∠A = ∠ACE, ∠B = ∠ECD, and then convert the sum of the three interior angles of the triangle into a flat