6.3Proving a Quadrilateral is a Parallelogram

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Define converse• What is the converse of this conditional?

• An angle is obtuse if its measure is between 90 and 180 degrees.

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Converse of Thm 6.3• If a quadrilateral is a parallelogram, then both

pairs of opposite sides are congruent.

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• If a quadrilateral is a parallelogram, then consecutive angles are supplementary.

Converse of Thm 6.4

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• If a quadrilateral is a parallelogram, then both pairs of opposite angles are congruent.

Converse of Thm 6.5

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• If a quadrilateral is a parallelogram, then the diagonals bisect each other.

Converse of Thm 6.6

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What must be true to make ABCD a parallelogram?

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What must be true to make ABCD a parallelogram?

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What must be true to make ABCD a parallelogram?

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What must be true to make ABCD a parallelogram?

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