sinx对称轴就是sinx取最值的地方
即x=kπ+π/2
所以这里kx/3+π/3=kπ+π/2
kx/3=kπ+π/6
x=3π+π/(2k)
x=π/6
3π+π/(2k)=π/6
3+1/(2k)=1/6
1/(2k)=-17/6
k=-3/17