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所谓的“8”字形图,是指形如图1所示的两个三角形,其中∠A OB和∠COD是对顶角,AB与CD是否平行无关紧要.根据三角形内角和定理,容易证明“8”字形图具有下面的性质:除对顶角外上下两个三角形中的另两个角之和相等,即∠A+∠B=∠C+∠D.利用这个性质可以轻松地求解一些“多角形”的内角和的问题.下面举例说明.
The so-called “8 ” glyph refers to the shape of the two triangles shown in Figure 1, where ∠A OB and ∠COD is the vertex angle, AB and CD is parallel does not matter .According to the triangle interior angle and theorem, easy Prove that the “8” glyph has the following properties: the sum of the other two corners of the upper and lower triangles except the vertex is equal, ie ∠A + ∠B = ∠C + ∠D. This property can easily be used to solve Some of the “polygons” inside the corner and the problem. Here’s an example.