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平行线分线段成比例定理及其推论是《相似形》一章中的重要定理,它是证明比例线段的重要方法.同学们对这个定理及其推论并不陌生,但真正能灵活运用它,还需要对它作深入的探讨.本文以课本一道复习题为例予以分析说明,以期抛砖引玉.题目:过△ABC的顶点C任作一直线,与边AB及中线AD分别交于点F和E.求证:AE:ED=2AF:
The proportional theorem and its inference of the parallel line segment are the important theorems in the chapter of “similarity”. It is an important method to prove the proportional line segment. Students are not strange to this theorem and its inference, but they can use it flexibly. It also needs to be discussed in depth. This article uses a textbook review question as an example to analyze and explain, with a view to throwing bricks to attract jade. Title: A vertex C of ΔABC is a straight line, and edge AB and midline AD are at points F and E respectively. . Proof: AE:ED=2AF: