ABCD is a parallelogram whose diagonals AC and BD intersect at O.
(i) Prove that △AOB≅△COD.
(ii) From the congruence proved in part (i), identify a new pair of equal sides that involves point O.
(iii) Using the equal side obtained in part (ii) together with a suitable angle, prove that △BOC≅△AOD.
(iv) Hence, state the common numerical relationship among the four segments AO,BO,CO and DO.