λέγω, ὅτι καὶ ὅλον τὸ ΑΓ ἑκατέρῳ τῶν ΑΒ, ΒΓ ἐστι σύμμετρον.
τὰ ΑΒ, ΒΓ. τὸ Δ ἄρα τὰ ΑΒ, ΒΓ, ΑΓ μετρεῖ· σύμμετρον ἄρα ἐστὶ τὸ ΑΓ ἑκατέρῳ τῶν ΑΒ, ΒΓ.
ὅτι καὶ τὰ ΑΒ, ΒΓ σύμμετρά ἐστιν.
σύμμετρα ἄρα ἐστὶ τὰ ΑΒ, ΒΓ.
Elementa. Euclid. ed. Johan Ludvig Heiberg. Leipzig. 1883-1888.
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