Proposition: 1.23: Constructing an Angle Equal to an Arbitrary Rectilinear Angle
(Proposition 23 from Book 1 of Euclid's “Elements”)
To construct a rectilinear angle equal to a given rectilinear angle at a (given) point on a given straight line.
Modern Formulation
It is possible to construct an angle $\angle{FAG}$ equal to an arbitrary angle $\angle{CDE}$ on an endpoint of a given segment $\overline{AB}.$
Table of Contents
Proofs: 1
Mentioned in:
Proofs: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Sections: 19
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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"