In the given figure, if AO = BO and OC = OD, then, ΔAOD ≅ ΔBOC by
In ΔAOD and ΔBOC, we have,
OA = OB (given)
OD = OC (given)
∠AOD = ∠BOC (vertically opposite angles)
Therefore, ΔAOD ≅ ΔBOC (by S.A.S. congruence condition)
Since ∠AOD and ∠BOC are the included angles for sides OA & OD and OB & OC respectively, we have the triangles congruent by using S.A.S. congruence rule.