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余弦定理是揭示三角形边角关系的重要定理．在解题中应用广泛，且蕴含有丰富的数学思想和方法．对它从不同的角度进行分析和挖掘，有助于数学能力的培养．现仅在平面几何中说明它的形式和应用．一、形式余弦定理ｃ２＝ａ２＋ｂ２－２ａｂｃｏｓＣ（仅以此式说明）中涉及到...
The cosine theorem is an important theorem for revealing the relationship between triangle corners. Widely used in problem solving, and contains a wealth of mathematical ideas and methods. It analyzes and excavates it from different angles and helps to develop mathematics ability. The form and application of it are only illustrated in plane geometry. First, the form of cosine theorem c2 = a2 + b2-2abcosC (only in this type of description) involved in ...