Proposition: 1.06: Isosceles Triagles II
(Proposition 6 from Book 1 of Euclid's “Elements”)
If a triangle has two angles equal to one another then the sides subtending the equal angles will also be equal to one another.
* Let $ABC$ be a triangle having the angle $ABC$ equal to the angle $ACB$.
* I say that side $AB$ is also equal to side $AC$.
Modern Formulation
If a given triangle has two equal angles, then the sides opposite the two angles are equal in length (i.e., the triangle is isosceles).
Table of Contents
Proofs: 1 Corollaries: 1
Mentioned in:
Proofs: 1 2 3 4 5 6 7 8 9 10 11
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References
Adapted from CC BYSA 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"
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"