Consider △ OEP and △ OFP
We know that
∠OEP = ∠OFP = 90o
OP is common i.e. OP = OP
From the figure we know that OP bisects ∠BPD
It can be written as
∠OPE = ∠OPF
By ASA congruence criterion
△ OEP ≅ △ OFP
OE = OF (c. p. c. t)
We know that AB and CD are equidistant from the centre
So we get
AB = CD
Therefore, it is proved that AB = CD.