相似形是初中几何的重要内容 ,有关线段成比例问题更是这部分习题的重中之重 .但是由于这部分内容概念性强 ,对应讲究 ,因而不少同学总会出现这样那样的错误 .我在批阅作业和试卷时发现一些常见错误 ,剖析如下 .一、忽视四条线段成比例时的顺序性已知线段ａ =2ｃｍ ,ｂ =4ｃｍ Similarity is an important content of junior high school geometry. The issue of proportioning segments is the most important part of this part of the exercise. However, because this part of the content is conceptually strong, the corresponding stress, many students will always appear this type of error. During the review of assignments and examination papers, some common mistakes were discovered and analysed as follows. I. Ignoring the orderliness of the four line segments when known in proportion: a = 2cm, b = 4cm