设多边形的内角和为S，边数为n，过多边形的一顶点引对角线，可把多边形分成（n-2）个三角形．根据三角形内角和定理可推出S=（n-2)·180”．根据这个公式，已知多边形的边数可求多边形的内角和；反过来，已知多边形的内角和也可以求多边形的边数．由于‘多边形的每一个内角与 Let the interior angle of the polygon be S and the number of edges be n. A vertex of the polygon may be a diagonal line, and the polygon may be divided into (n-2) triangles. According to the triangle inner angle and theorem, S = (n-2) · 180" can be deduced. According to this formula, the number of sides of a known polygon can be calculated as the inner angle of a polygon and, in turn, the interior angle of a known polygon and the side of a polygon can also be found. Number. Due to each interior angle of the polygon