f（x）=√3/2sin2x-cos∧2-1/2
=√3/2sin2x-(1+cos2x)/2-1/2
=√3/2sin2x-1/2cos2x-1
=cosπ/6sin2x-sinπ/6cos2x-1
=sin(2x-π/6)-1
sin(2C-π/6)-1=0
sin(2C-π/6)=1
2C-π/6=π/2
2C=2π/3
C=π/3
又向量m=（1,sinA）与向量n=（2,sinB）共线
所以
1/2=sinA/sinB
由正弦定理a/b=1/2
b=2a
利用余弦定理
c²=a²+b²-2abcosC
3=5a²-4a²×1/2
=3a²
a²=1
a=1
b=2a=2
所以
a=1
b=2