Definition: 1.12: Acute Angle
And an acute angle (is) one less than a right angle.
Modern Definition
Euclid's definition corresponds to today's formulation.
Example
The angle \(\angle{PQR}\) (marked dark-green) is acute.
Mentioned in:
Definitions: 1 2 3 4
Proofs: 5 6 7 8
Propositions: 9 10 11 12
Thank you to the contributors under CC BY-SA 4.0! 
- Github:
-
- non-Github:
- @Fitzpatrick
References
Adapted from (subject to copyright, with kind permission)
- Fitzpatrick, Richard: Euclid's "Elements of Geometry"
