Lemma: Lem. 12.02: Areas of Circles are as Squares on Diameters

(Lemma to Proposition 2 from Book 12 of Euclid's “Elements”)

So, I say that, area $S$ being greater than circle $EFGH$, as area $S$ is to circle $ABCD$, so circle $EFGH$ (is) to some area less than circle $ABCD$.

fig02e

Modern Formulation

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Proofs: 1

Proofs: 1 2 3 4


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References

Adapted from (subject to copyright, with kind permission)

  1. Fitzpatrick, Richard: Euclid's "Elements of Geometry"