高一三角函数,急急~求(2SIN80
求(2SI0-SIN20)/SIN70的值 上面都是角度~
(2sin80-sin20)/sin70 =[2sin(20+60)-sin20]/sin70 =(2sin20cos60+2cos20sin60-sin20)/sin70 =(sin20-sin20+√3cos20)/sin70 =√3cos20/sin70 =√3sin70/sin70 =√3