T/4=7π/12-π/3故T=πw=2f(π/3)=1故2π/3+φ=π/2+2kπ|φ|<π/2故φ=-π/6所以f(x)=sin(2x-π/6)(2)当x属于[π/6,5π/12]时,得到2x-π/6属于[π/6,2π/3]画出sinx在[π/6,2π/3]上的图像线y=a与函数f(x)的图像有两个交点得到√3/2<=a<1