Proof: Parallel Then Parallelogram

Let's prove the following theorem:

Proof:

Proof Table

#	Claim	Reason
1	BD || AC	if DB || CA, then BD || AC (Parallel Lines Property 2)
2	AC || BD	if BD || AC, then AC || BD (Parallel Lines Property 3)
3	ABDC is a parallelogram	if AB || CD and AC || BD, then ABDC is a parallelogram (Parallelogram Property)

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