y=2tan(π/6-1/2x)=- 2tan(1/2x -π/6)
1/2x -π/6=kπ,或1/2x -π/6=kπ+π/2,k∈Z
X= 2kπ+π/3,或X=2kπ+4π/3
所以该函数的对称中心为：
(2kπ+π/3,0),( 2kπ+4π/3,0) ,k∈Z.