构成三角形的三边的长度是互相制约的 ,不是任意三条线段都可构成三角形的。只有满足三角形三边关系定理“三角形两边之和大于第三边”及其推论“三角形两边的差小于第三边”的三条线段 ,才能构成三角形。灵活运用三边关系 ,可简捷地解决以下两类问题。一、判断三条线段能否组 The lengths of the three sides that make up the triangle are mutually constrained, and not any three line segments can form a triangle. Only if the three-side triangle relation theorem “The sum of the sides of the triangle is greater than the third side” and the inference that “the difference between the two sides of the triangle is smaller than the third side” can satisfy the triangle. The flexible use of the trilateral relationship can easily solve the following two types of problems. First, determine whether the three line segments can be grouped