Diagnols AC and BD of a trapezium ABCD with AB II DC intersect each other at O. Prove that ar(AOD) = ar(BOC).(figure not given)

This question was asked in Ex 9.3, 8

Diagnols AC and BD of a trapezium ABCD with AB II DC intersect each other at O. Prove that ar(AOD) = ar(BOC).
(figure not given)