Corollary: Triangulation of Quadrilateral and Sum of Angles
(related to Proposition: 1.32: Sum Of Angles in a Triangle and Exterior Angle)
Since a quadrilateral can be divided into two triangles, the sum of its angles equals four right angles.
\[\sum_{i=1}^6 \alpha_i=2\times 180^\circ=4\times 90^\circ\]
![triangle3](https://github.com/bookofproofs/bookofproofs.github.io/blob/main/_sources/_assets/images/examples/triangle3.jpg?raw=true)
Table of Contents
Proofs: 1
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References
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"