f(x)=[√ (a²+b²)]sin(wx+m),其中tanm=b/a,
T=π=2π/|w|,w>0,即w=2
(π/12)*2+m=π/2+2kπ,k是整数,即m=π/3+2kπ
√ (a²+b²)=4
综上,得
f(x)=4sin[(π/6)x+(π/3)]