分类：教育/科学-学习帮助
问题：寒假作业,急急急,高手进4cos35*cos35
4c35*cos35-cos170-tan160sin170请给出详细过程
回答：4(cos35)^2-cos170-tan160sin170
=2*2(cos35)^2-cos170-sin160/cos160*sin170
=2(1+cos70)-(cos170cos160+sin170sin160)/cos170
=2+2cos70-cos(170-160)/(-cos20)
=2+2sin20+cos10/cos20
=2+(2sin20cos20++cos10)/cos20
=2+(sin40+sin80)/cos20
=2+2sin60cos20/cos20
=2+2sin60
=2+√3.