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同学们运用相似三角形的性质解题时,由于概念理解不准确、对应关系分不清、或考虑不全面等原因而出错,下面就一些常见的错误加以剖析.易错点一、对应边判断错误例1如图,△ADE~△ABC,AD=3cm,AE=2cm,CE=4cm,BC=9cm,求:BD、DE的长.错解:由题意得:AD/AB=AE/CE=DE/BC,3/AB=2/4=DE/9,得AB=6(cm)DE=4.5(cm).剖析:相似三角形的对应边成比例,边的对应,没有到位,找错了对应边,AE与CE不是对应边.
Students use the nature of similar triangles to solve the problem, due to inaccurate understanding of the concept of correspondence can not tell, or consider the reasons for incomplete and other mistakes, the following some common mistakes to be analyzed. Example 1 As shown in the figure, △ ADE ~ △ ABC, AD = 3cm, AE = 2cm, CE = 4cm, BC = 9cm, = DE / BC, 3 / AB = 2/4 = DE / 9, AB = 6 (cm) DE = 4.5 (cm). Analysis: Similar triangles corresponding to the side of the proportion, the corresponding edge, Corresponding edge, AE and CE is not the corresponding side.