(tan5°-tan85°)*cos70°/(1+sin70°)

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(tan5°-tan85°)*cos70°/(1+sin70°)
(tan5°-tan85°)*cos70°/(1+sin70°)

(tan5°-tan85°)*cos70°/(1+sin70°)
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

=-2cos10/sin10*sin10*cos10/(1+sin70) =-2*(1+cos20)/(1+sin70) =-2 原式= (tan5 - cot5)* (1-sin70)/cos70 = (sin5/cos

tan5=0.08748866352592401
tan85=11.43005230276132
cos75=0.25881904510252074
sin70=0.9396926207859083
自己算吧

(tan5°-tan85°)*cos70°/(1+sin70°)
=(sin5/cos5-cos5/sin5)sin20/(1+cos20)
=2(sin^2 5 -cos^2 5)/sin10 (2sin10cos10/cos^2 10)
=-4cos10/sin10 * sin10/cos10
=-4