一、平行线型如图1和图2,DE∥BC,则△ABC∽△ADE.像这样,有一边互相平行的相似三角形叫做平行线型相似三角形.由于图1外形上极像大写字母A,故我们称图1为A型图,由于图2外形上极像大写字母X,故我们称图2为X型图.其中A型图可得相关比例式:(1)DABD=EACE;(2)AADB=AACE=BDCE.X型图可 First, the parallel line type is shown in Fig. 1 and Fig. 2, DE ∥ BC, then △ ABC ∽ △ ADE. Like this, similar triangles with one side parallel to each other are called parallel line type similar triangles. Since Fig. 1 is very much like a capital letter A Therefore, we call Figure 1 an A-type diagram. Since Figure 2 is very similar to the uppercase letter X, we call Figure 2 an X-type diagram. Among them, the A-type diagram can be related to the ratio: (1) DABD=EACE; 2) AADB=AACE=BDCE.X type map can be