判定三角形相似的定理:平行于三角形一边的直线和其他两边相交,所构成的三角形与原三角形相似.位似图形的概念:两个多边形不仅相似,而且对应顶点的连线相交于一点,对应边互相平行,像这样的两个图形叫位似图形,这个点叫位似中心.以上是人数版九年级数学第二十七章《相似》一章中第42页的判定三角形相似的定理和第59—60页的位似图形的概念.笔者认为这个定理和概念叙述的 Triangle to determine the similarity of the theorem: parallel to one side of the triangle line and the other two intersect, the triangle formed by the original triangle similar to the concept of bit-like graphics: not only the two polygons similar, and the corresponding vertices of the line intersect at one point, the corresponding edge Parallel to each other, like this two graphics called bit-like graphics, this bit is bit like a center .This is a number of ninth grade mathematics chapter twenty-seventh chapter “similar” chapter 42 of the judgment triangle similarity theorem and The concept of bit-like graphics on pages 59-60. I consider this theorem and concept narrative