From a uniform circular disc of radius 2 cm (its centre of mass is at 'O') a circular portion of radius 1 cm is removed such that the shift in centre of mass is maximum. The disc is now rotated by an angle θ about an axis perpendicular to its plane and passing through 'O'. If the magnitude of displacement of new centre of mass is \(\frac{1}{\sqrt3}\) cm, then the θ is