(tan5°-tan85°)*cos70°/(1+ - 知识问答

(tan5°-tan85°)*cos70°/(1+sin70°)

4个回答

原式=(sin5/cos5-cos5/sin5)cos70/(1+sin70)
=[(sin5)^2-(cos5)^2]/sin5/cos5*cos70/(1+sin70)
=-2cos10/sin10*sin20/(1+sin70)
=-2cos10/sin10*sin10*cos10/(1+sin70)
=-2*(1+cos20)/(1+sin70)
=-2

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