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§1 基本公式要点:七种基本公式及公式的变形与逆用。例1 求证2sin(π/4+α)sin(π/4-α)=cos2α。分析:本题虽可将左式用和角公式或积化和差公式化简得到右式,但都比较繁,若注意
§1 Essential points of the basic formula: The transformation and inverse use of the seven basic formulas and formulas. Example 1 Proof 2sin(π/4+α)sin(π/4-α)=cos2α. Analysis: Although this question can be used to simplify the left-hand use and angle formula or product and difference formula to get the right-form, but it is more complicated, if attention