Lemma: Lem. 10.021: Medial is Irrational
(Lemma to Proposition 21 from Book 10 of Euclid's “Elements”)
If there are two straight lines then as the first is to the second, so the (square) on the first (is) to the (rectangle contained) by the two straight lines.
Modern Formulation
(not yet contributed)
Table of Contents
Proofs: 1
Mentioned in:
Proofs: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Thank you to the contributors under CC BYSA 4.0!
 Github:

 nonGithub:
 @Fitzpatrick
References
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"