In the **previous post**, we have proved that if the opposite sides of a quadrilateral are congruent, then they are parallel. In this post, we are going to show that if the opposite angles of a quadrilateral are congruent, then it is a parallelogram.

In the figure below, we have quadrilateral ABCD with and . To show that it is a parallelogram, we have to show that and .

**Theorem:** If two pairs of opposite angles of a quadrilateral are congruent, then it is a parallelogram.

**Proof**

It is given that and . Continue reading…