Opposite sides and opposite angles of a parallelogram are equal in measure. The theorem states that in a parallelogram ABCD, the length of side AB equals the length of side DC, and the length of side AD equals the length of side BC. Additionally, the measure of angle BAC equals the measure of angle BAD.

1. Parallelograms

2. Theorem: Opposite sides and opposite angles of a parallelogram are respectively equal in measure Given: A parallelogram, abcd. b c a d

3. To prove: |ab| = |dc| and |ad| = |bc| (opposite sides); |<bad| = |<bac| (opposite angles).