If O is (0,0), A is (1,0), and B is (1/2, √3/2), then what is the center of the circle for which the lines OA, OB, and AB are tangents?
a) (1/2, 1/√3)
b) (1/√3, 1/2)
c) (1/2, √3/2)
d) (√3/2, 1/2)