$$\(19 O A B\)$$ is a triangle. The point $$\(C\)$$ lies on $$\(O A\)$$ such that $$\(O C: C A=1: 2\)$$ The point $$\(D\)$$ lies on $$\(O B\)$$ such that $$\(O D: D B=1: 2\)$$ Using a vector method, prove that $$\(A B D C\)$$ is a trapezium.

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