设其为Asin(wx+b)
w=2π/T=2π/π=2
A=3
sinx的对称轴为x=kπ+π/2;k属于Z
2x+b=kπ+π/2
x=(kπ+π/2-b)/2
则sin(2x+b)对称轴为x=(kπ+π/2-b)/2
x=(kπ+π/2-b)/2=π/6
b=kπ+π/2-π/3
=kπ+π/6
取k=0,b=π/6
原函数为3sin(2x+π/6)