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在中考和一些竞赛中,有一些与三角形有关的题目,若用其他方法做是很难一下子解决的,但是用面积法来做则十分简捷,能收到化难为易、事半功倍之效.现举例说明如下,希望对同学们能有所启发.一、利用面积相等的性质解题例1如图1,在直角△ABC中,AB=13,AC=12,BC=5.求AB边上的高CD的长.解析:因为S△ABC=1/2AB×CD,又S△ABC=1/2AC×BC,所以1/2AB×CD=1/2AC×BC,即13×CD=12×5.解
In the senior high school entrance exams and some contests, there are some problems related to triangles that can not be resolved easily by other methods. However, using the area method is very simple and can achieve the goal of reducing costs and expending more energy. An example of the following, I hope the students can be inspired. First, the use of the same area of ?? the nature of the solution 1 as shown in Figure 1, at a right angle ABC, AB = 13, AC = 12, BC = 5. CDA = 1 / 2AC × BC, that is, 13 × CD = 12 × S × ABC = 1 / 2AB × CD and S △ ABC = 1 / 2AC × BC 5. Solution