对于某些几何问题,常常需要适当的辅助线才能快速获证.特别是当题目中有平行线或添加了平行线时,此时只要想到科用平行线有关的定理,也就找到了解题的突破口,为顺利解题奠定了基础.下面举例分析,一定会对同学们有所启迪.题目如图1所示,DF∥AB,C为DF上的点,四边形ACED是平行四边形,求证:BF=EF. For some geometric problems, often need the appropriate auxiliary line to obtain fast certification.Especially when the topic has parallel lines or added parallel lines, this time as long as you think of the line with the relevant theorem, also find the problem The breakthrough point for the smooth solution to the problem laid the foundation.Analysis of the following example, it will be enlightenment to the students.The subject is shown in Figure 1, DF∥AB, C for the DF on the point, quadrilateral ACED is a parallelogram, verify: BF = EF.