Corollary: Parallelogram - Defining Property I
(related to Proposition: 1.34: Opposite Sides and Opposite Angles of Parallelograms)
If both pairs of opposite sides of a 4-sided figure are equal in length, it is a parallelogram.
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Thank you to the contributors under CC BY-SA 4.0!
Adapted from CC BY-SA 3.0 Sources:
- Callahan, Daniel: "Euclid’s 'Elements' Redux" 2014
Adapted from (Public Domain)
- Casey, John: "The First Six Books of the Elements of Euclid"