求4cos^2(35`)-cos(170`)-tan(160`)sin(170`)的值

问题描述:

求4cos^2(35`)-cos(170`)-tan(160`)sin(170`)的值

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