Steps of Construction:
(i) Construct a regular hexagon ABCDEF with each side equal to 4 cm.
(ii) Draw any two main diagonals of the hexagon. Let them meet at a point O.
(iii) With O as centre and OA as radius draw a circle which will pass through all the vertices of the hexagon.
( iv) This is the required circumcircle. Measure OA.
(v) OA = 4 cm