## 10 Parallelogram Theorems - You Must Know

Theorem 1: A diagonal of a parallelogram divides it into two congruent triangles.
See proof here

Theorem 2: In a parallelogram, opposite sides are equal.
See proof here

Theorem 3: If each pair of opposite sides of a quadrilateral is equal, then it is a parallelogram.
See proof here

Theorem 4: In a parallelogram, opposite angles are equal
See proof here

Theorem 5: If each pair of opposite angles of a quadrilateral is equal, then it is a parallelogram.
See proof here

Theorem 6: If a pair of opposite sides of a quadrilateral is equal and parallel, then it is a parallelogram.
See proof here

Theorem 7: If a pair of opposite sides of a quadrilateral is equal and parallel, then it is a parallelogram.
See proof here

Theorem 8: If the diagonals of a quadrilateral bisect each other, then it is a parallelogram.
See proof here

Theorem 9: Mid-point theorem
The line segment joining the mid-points of any two sides of a triangle is parallel to the third side and is equal to half of it.
See proof here

Theorem 10: Converse of mid-point theorem  #### 1 comment:

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