tan9+cot9-cot27-tan27

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9,27是9°,27°的话答案是 4tan9+cot9-cot27-tan27=sina9/cos9+cos9/sin9-(sin27/cos27+cos27/sin27)=1/(sin9cos9)-1/(sin27cos27)=2/sin18-2/sin54=2(sin54-sin18)/(sin18sin54)=2*2con36sin18/(sin18sin54)=4