| Statements | Reasons |
| 1. Parallelogram ABCD | Given |
| 2. \(\overline{AD}\parallel\overline{BC}\) \(\overline{AB}\parallel\overline{CD}\) | Definition of a Parallelogram |
| 3. \(m\angle B+m\angle A=180^{\circ}\) \(m\angle B+m\angle C=180^{\circ}\) | Same-Side Interior Angles Theorem |
| \(\angle A\quad\text{and}\quad\angle B\quad\text{are supplementary.}\)\(\angle B\quad\text{and}\quad\angle C\quad\text{are supplementary.}\) | Definition of supplementary angles. |
| Statements | Reasons |
| 1. Parallelogram ABCD | Given |
| 2. \(\overline{AD}\parallel\overline{BC}\) \(\overline{AB}\parallel\overline{CD}\) | Definition of a Parallelogram |
| 3. \(m\angle B+m\angle A=180^{\circ}\) \(m\angle B+m\angle C=180^{\circ}\) | Same-Side Interior Angles Theorem |
| \(\angle A\quad\text{and}\quad\angle B\quad\text{are supplementary.}\)\(\angle B\quad\text{and}\quad\angle C\quad\text{are supplementary.}\) | Definition of supplementary angles. |