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正余弦定理在判定三角形的形状的时候通常有两种途径:一是将题目中的边化为角,一是将角化为边,二者在解决三角形形状的判定时有着异曲同工之妙.另外,题目中如果只是三角(或者两角)及其线性组合的正余弦之间的关系,也可以直接应用三角恒等变形中的相关公式直接解题.以下是几个例子.例1在△ABC中,若acosA=bcosB,则△ABC的形状是()(A)等腰三角形(B)直角三角形
Sine and cosine theorem in judging the shape of the triangle there are usually two ways: First, the subject of the edge of the corner, one is the corner of the side, both in the determination of the shape of the triangle has the same purpose. , If the subject is only the triangle (or two corners) and the linear combination of the relationship between the cosine, can also be directly applied to the equation of isostrophism deformation directly solve the problem. Here are a few examples. Example 1 △ ABC , If acosA = bcosB, the shape of ABC is () (A) Isosceles triangle (B) Right triangle