等比式和等积式既是几何证明中的重点,又是难点.本文结合实例向同学们介绍这类问题的几种常见的解法,供参考.一、基本方法——确定相似三角形即查证等比式(等积式先化成等比式)每端(或前项、后项)所含的字母,看它们能否分别表示两个形状相同的三角形的顶点.若能,则证明它们相似.例1如图1,△ABC中,∠BAC=90°,BC的垂线交BC于D,交 Equal formula and the same is not only the geometric proof of the focus, but also difficult.This article with examples to introduce students to several common solutions to these problems for reference.First, the basic method - to determine similar triangles that verification Let us look at the letters in each end (or in the preceding paragraph, or in the back) of the equation (Equal Sum Prior Equalization) to see if they represent the vertices of the triangles of the two identically shaped triangles, and if so, prove that they are similar. Example 1 shown in Figure 1, △ ABC, ∠ BAC = 90 ° BC vertical BC BC in D, AC