cosa=3/5，0cos(a-π/6)=cosacos(π/6)+sinasin(π/6) =(3/5)(√3/2)+(4/5)(1/2) =(4+3√3)/10祝你开心！希望能帮到你，如果不懂，请追问，祝学习进步！O(∩_∩)O
cos(a-π/6)=cosa*cosπ/6+sina*sinπ/6=3/5*√3/2+4/5*1/2=(3√3+4)/10
3√3)/10+2/5
