8.3Proving a Quadrilateral is a Parallelogram
Quick Answer
Five ways to prove a quadrilateral is a parallelogram: (1) both pairs of opposite sides parallel, (2) both pairs of opposite sides congruent, (3) one pair of sides both parallel and congruent, (4) diagonals bisect each other, (5) both pairs of opposite angles congruent.
Essential Question
Why are there five different sufficient conditions for proving a quadrilateral is a parallelogram, and how do you choose the right one?
Learning Goals
- 1State the five conditions sufficient to prove a parallelogram.
- 2Apply each condition in a proof or problem.
- 3Use coordinate methods to prove a quadrilateral is a parallelogram.
Key Vocabulary
Sufficient condition
A condition that, if true, guarantees the conclusion — here, that the quadrilateral is a parallelogram.
Full lesson content coming soon
Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.