a为锐角,cos(a+π/6)=3/5则:sin(a+π/6)=4/5sin(a-π/12)=sin[(a+π/6)-π/4] =sin(a+π/6)cos(π/4)-cos(a+π/6)sin(π/4) =(4/5)(√2/2)-(3/5)(√2/2) =√2/10 祝你开心!希望能帮到你,如果不懂,请追问,祝学习进步!O(∩_∩)O