证明两条线段相等是平面几何中最常见的问题．现就初二年级学过的各种常用方法，归纳介绍如下．一、利用全等三角形的性质证明例△ABC中A＝6f°，B和C的平分线BD、CE相交于O．求证：OD＝OE．分析如图1，连结AO，则AO平分ZA．从而OygAB、AC的距离相等．作OF上AC于F，OC上AB于C， It is proved that the equality of two line segments is the most common problem in plane geometry. The various commonly used methods learned in the second grade are summarized below. First, the use of congruent triangles to prove the nature of the case △ ABC A = 6f °, B and C bisector BD, CE intersect at O. Proof: OD=OE. The analysis is shown in Fig. 1. If AO is linked, AO divides ZA. Thus, the distance between OygAB and AC is equal. For OF on AC on F, OC on AB on C,