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全等三角形是初中几何中的一个重要内容,也是初中生必须掌握的三角形方面的两大知识点(全等和相似)之一.在解决几何问题时,若能根据图形的特征添加适当的辅助线,构造出全等三角形,并灵活运用全等图形的性质,往往可以使问题化难为易.现列举几例.供大家参考.一、见角平分线试折叠例1如图1,在△ABC中,AD平分∠BAC,AB+BD=AC.求证:∠B:∠C=2:1.
The congruent triangle is one of the important contents of junior high school geometry and also one of the two major knowledge points (congruent and similar) in the triangle that junior high school students must master.In the process of solving the geometric problem, if the appropriate auxiliary can be added according to the characteristics of the graphic Line, the construction of congruent triangles, and the flexibility to use the nature of congruent graphics can often make the problem difficult for the easy. Now give a few examples for your reference. First, the angle bisector fold test case 1 as shown in Figure 1, △ ABC, AD bisect ∠ BAC, AB + BD = AC. Prove: ∠ B: ∠ C = 2: 1.