你公式?jīng)]背好,sin(x-y)=sin(x+(-y))=sinxcos(-y)+cosxsin(-y),sinx為奇函數(shù),cosx為偶函數(shù),所以
cos(-y)=cosy,sin(-y)=-siny,所以sin(x-y)=sinxcosy-cosxsiny,這里
-cos（π/6）sinx+sin（π/6）cosx=sin（π/6）cosx-cos（π/6）sinx,對(duì)照上面我推倒的公式可以看出結(jié)果為sin（π/6-x）.
另外根據(jù)你說(shuō)的輔助角的cosθ=-√3/2,sinθ=1/2 θ應(yīng)該為5π/6+2kπ,-π/6的正弦為-1/2,不是1/2