## Helpful Links

## Theorems

**Prove a Quadrilateral is a Parallelogram by one of the following**

**Definition:** The quadrilateral has **2 pairs** of parallel sides. (same slope!)

**Theorem 1:** The opposite sides are congruent

**Theorem 2:** The opposite angles are congruent

**Theorem 3:** The diagonals bisects each other.

**Theorem 4:** The consecutive angles are supplementary.

**Theorem 5:** **One** pair of sides are both parallel (same slope) and congruent.

## Helpful Video

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