相似三角形从基本图形的构成上,可分成三个基本类型:平行线型、相交线型和旋转型. 一、平行线型相似三角形平行线型是由两条平行线与其他直线配合构成的两个相似三角形,这种类型的相似三角形的对应元素比较明显,对应边、对应角、对应顶点有同样的顺序性,对应边平行或重合,如图1所示. Similar triangles can be divided into three basic types from the basic pattern: parallel lines, intersecting lines, and rotations. 1. Parallel lines Similar triangles Parallel lines are two parallel lines and other lines. Similar triangles, the corresponding elements of this type of similar triangles are obvious, the corresponding edges, corresponding angles, and corresponding vertices have the same sequence, and the corresponding edges are parallel or coincident, as shown in Figure 1.