求4cos^2(35`)-cos(170`)-tan(160`)sin(170`)的值
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求4cos^2(35`)-cos(170`)-tan(160`)sin(170`)的值
![求4cos^2(35`)-cos(170`)-tan(160`)sin(170`)的值](/uploads/image/z/17469853-61-3.jpg?t=%E6%B1%824cos%5E2%2835%60%29-cos%28170%60%29-tan%28160%60%29sin%28170%60%29%E7%9A%84%E5%80%BC)
原式=2(1+cos70)+cos10+tan20sin10
=2+2sin20+cos10+sin20sin10/cos20
=2+(2sin20cos20+(cos10cos20+sin20sin10))/cos20
=2+(sin40+cos10)/cos20
=2+(sin40+sin80)/cos20
=2+2sin60cos20/cos20
=2+根号3
=2+2sin20+cos10+sin20sin10/cos20
=2+(2sin20cos20+(cos10cos20+sin20sin10))/cos20
=2+(sin40+cos10)/cos20
=2+(sin40+sin80)/cos20
=2+2sin60cos20/cos20
=2+根号3
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