Quadrilaterals with Congruent Opposite Angles are Parallelograms

In last week’s post, we have learned that quadrilaterals with congruent opposite sides are parallelograms. In this post, we show a related theorem. That is, quadrilaterals whose opposite angles are congruent are parallelograms. In the figure above, is a quadrilateral where and are congruent and and are congruent. In proving the theorem, we need to […]
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