相似三角形内容是在初中平面几何基础知识上的进一步拓展与提升,包括相似三角形的定义、判定、性质等,其中特殊的直角三角形相似的判定及直角三角形的射影定理是平面几何的重要知识之一,我们可以根据不同的已知条件,选择恰当的判定定理来判定两个三角形是否相似,也可以利用相似三角形的性质来解决一些问题。下面笔者结合例题进行说明,与读者交流。 Similar triangle content is further expanded and promoted in basic geometry of junior high school, including the definition, judgment and nature of similar triangles. The special similarity judgment of right triangle and the projection theorem of right triangle are one of the important knowledge of plane geometry , We can determine the similarity of two triangles according to different known conditions and choose the appropriate judgment theorem. We can also use the similar triangles to solve some problems. The following combination of examples to illustrate the author, and readers exchange.