本文所述的封闭折线,若无特别声明,都是指空间封闭折线(包括平面封闭折线在内)。 定义1 封闭折线A_1A_2A_3…A_nA_1的任意两条相邻的边所成的劣角(小于平角的角),称为这条封闭折线的顶角,顶点为A_i的顶角记作∠A_i(i=1,2,…,n)。 定义2 所有顶角都相等的封闭折线,称为等角闭折线;否则,就称为非等角闭折线。 The enclosed polyline described in this article, unless otherwise stated, refers to the space enclosed polyline (including the planar enclosed polyline). Definition 1 The inferior angle (angle less than the angle of flat corner) enclosed by any two adjacent edges of the closed polyline A_1A_2A_3...A_nA_1 is called the vertex angle of this closed polyline, and the vertex whose vertex is A_i is denoted as ∠A_i (i= 1,2,...,n). Definition 2 A closed polyline with equal apex angles is called an isostatic closing line; otherwise, it is called a non-isogonal closing line.