sina-√3cosa=m-1
(1/2)sina-(√3/2)cosa=(m-1)/2
sinacos(π/3)-cosasin(π/3)=(m-1)/2
sin(a-π/3)=(m-1)/2
-1≤sin(a-π/3)≤1
-1≤(m-1)/2≤1
-2≤m-1≤2
-1≤m≤3
m的取值范围为[-1,3]