a*b=sinx*2cosx+(√3cosx-√3sinx)(cosx-sinx)
=sin2x+√3(cos²x-sin²x)
=sin2x+√3cos2x
=2sin(2x+π/3)
f(x)=a*b*L=2Lsin(2x+π/3)
f(π/12)=1=2Lsin(2π/12+π/3)
=2Lsin(π/2)=2L
=> L=1/2
∴f(x)=sin(2x+π/3)
f(x)的单调递增区间为-π/2≤2x+π/3≤π/2
解得 -5π/12≤x≤π/12
∴f(x)的单调递增区间为[-5π/12,π/12]