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Parallelograms
A
B
C
D
E
. . . .

Properties of Parallelograms (1)

Theorem.
Consecutive angles in a parallelogram are supplementary.

Given: Parallelogram ABCD
Prove: ∠A and ∠B are supplementary.
∠B and ∠C are supplementary.
∠C and ∠D are supplementary.
∠D and ∠A are supplementary.


Proof: