本文所讨论的封闭折线，都是平面封闭折线．定义1设M是封闭折线A2A2A3…AnA1所在平面内的定点．，动点P沿着这条析线的边A2A2，A2A3，…，AnA1依次行进，若定点M始终处于动点P行进方向的左侧（或右侧），则点M称为这条封闭折线的左侧点（或右侧．戈）．左侧点与右侧点统称为同 The closed polyline discussed in this paper is a flat closed polyline. Definition 1 Let M be the fixed point in the plane of the enclosed polyline A2A2A3...AnA1. The moving point P runs along the edges A2A2, A2A3,..., AnA1 of this analysis line. If the fixed point M is always on the left side (or the right side) of the moving direction of the moving point P, the point M is called this closed folding line. The left side of the point (or right side. Ge). The left and right points are collectively referred to as