多边形的内角和定理的引入是建立在三角形内角和定理和四边形内角和定理的基础上的 ,利用四边形的对角线把四边形内角和问题转化成三角形内角和 ,从而证明了四边形内和定理 .继续对五边形、六边形的内角和进行分析推导 ,从而发现规律 ,得出结论 ,进一步扩展归纳得出 :经过ｎ边 The introduction of inner angles and theorems of polygons is based on triangle inner angles and theorem and quadrilateral inner angles and theorems. Quadrilateral inner angles and problems are transformed into triangle inner angle sums using quadrilateral diagonals, thus the quadratic inner sum theorem is proved. The internal angles of pentagons and hexagons are analyzed and deduced, so that the law is found and the conclusions are drawn. Further extensions are drawn: After n edges