1. ABCD is a rectangle
1. given
2. draw AC and BD
2. unique line postulate
3. ∠BAD and ∠CDA are right angles
3. def. of a rectangle
4. ∠BAD ≅ ∠CDA
4. all right angles are congruent
5. ABCD is a parallelogram
5. def. of a rectangle
6. AB ≅ CD
6. ♣
7. AD ≅ AD
7. reflexive property
8. △BAD ≅ △DCB
8. ♦
9. BD ≅ AC
9. ♠