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余弦定理是揭示三角形边角关系的重要定理,直接运用它可解决一类已知三角形两边及夹角求第三边或者是已知三个边求角的问题,若对余弦定理加以变形并适当移于其他知识,则使用起来更为方便、灵活.
The cosine theorem is an important theorem that reveals the relationship between triangle edges and corners. It can be directly used to solve the problem that the sides of a given type of triangle and the included angle are calculated on the third side or the known three sides. If the cosine theorem is modified and appropriate Move to other knowledge, it is more convenient and flexible to use.