Definition:Euclid's Definitions - Book I/10 - Right Angle
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Definition
In the words of Euclid:
- When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that on which it stands.
(The Elements: Book $\text{I}$: Definition $10$)
Sources
- 1926: Sir Thomas L. Heath: Euclid: The Thirteen Books of The Elements: Volume 1 (2nd ed.) ... (previous) ... (next): Book $\text{I}$. Definitions