众所周知,在任意三角形中,均有: 性质一:任意两边之和大于第三边; 性质二:任意两边之差小于第三边。在国内外的大学入学试题中,在国际中学生数学竞赛试题中,常有一些试题,要用“三条线段围成三角形的充要条件”来解。试问:用三条线段为边、围成三角形的充要条件是什么呢? As we all know, in any triangle, there are: Property 1: The sum of any two sides is greater than the third side; Property 2: The difference between any two sides is smaller than the third side. In the domestic and foreign university entrance examination questions, there are often some questions in the international middle school students mathematics competition test questions, which should be solved by using “the necessary and sufficient conditions for the three line segments to form a triangle”. What is the necessary and sufficient condition for using triangles as edges and triangles?