Synagoge

103 Καὶ τούτοις ἀκολούθως δύο τῶν Ε∠ ∠Μ δοθεισῶν ληψόμεθα τὰς δύο μέσας ἀνάλογον ἐν τῇ συνεχεῖ ἀναλογίᾳ. ἐκκείσθωσαν γὰρ ταῖς Ε∠ ∠Ζ ∠Μ ἴσαι αἱ Ε∠ ∠Ζ ∠Μ. καὶ ἐπεὶ δέδεικται ὡς τὸ ἀπὸ τῆς Ε∠ πρὸς τὸ ἀπὸ τῆς ∠Ζ, οὕτως ἡ ∠Ζ πρὸς τὴν ∠Μ, δῆλον ὡς ἡ ∠Μ οὐκ ἔστι τρίτη ἀνάλογον τῶν Ε∠ ∠Ζ.

Εἰ γὰρ δυνατόν, ἔστω ἡ ∠Μ τρίτη ἀνάλογον τῶν Ε∠ ∠Ζ. ἐπεὶ οὖν ἡ ∠Μ τρίτη ἀναλογόν ἐστι τῶν Ε∠ ∠Ζ, ἔστιν ὡς ἡ Ε∠ πρὸς τὴν ∠Ζ, οὕτως ἡ ∠Ζ πρὸς τὴν ∠Μ· καὶ ὡς ἄρα τὸ ἀπὸ τῆς Ε∠ πρὸς τὸ ἀπὸ τῆς ∠Ζ, οὕτως ἡ Ε∠ πρὸς ∠Μ, ἀλλʼ ἦν ὡς τὸ ἀπὸ τῆς Ε∠ πρὸς τὸ ἀπὸ τῆς ∠Ζ, οὕτως ἡ ∠Ζ πρὸς ∠Μ· διʼ ἴσου ἄρα ἐστὶν ὡς ἡ Ε∠ πρὸς τὴν ∠Μ, οὕτως ἡ ∠Ζ πρὸς τὴν ∠Μ· ἑκατέρα ἄρα τῶν Ε∠ ∠Ζ πρὸς τὴν ∠Μ τὸν αὐτὸν ἔχει λόγον· ἴση ἄρα ἐστιν ἡ Ε∠ τῇ ∠Ζ, ὅπερ [*](1. 2. ἄλλως ἡ ΛΚ A1, corr. man. rec. (BS) 2. 3. ἄρα ΕΚ AS, ἡ add. B Guelf. 6. τῆς (ante ∠Ζ) om AB1S, Add. B3 et, ut vi- detur, Guelf. 10. γωνίας τὰς ὑπὸ ΞΛ∠ ΛΑΞ ABS, γωνίας τὰς ὑπὸ ξλδ λδξ V2, corr. Bredow 11. ταῖς ὑπὸ ζδη V2 Sca Bredow pro ταῖς ὑπὸ Ξ∠Η 12. λοιπαῖς ἴσαις AB1S, corr. B3 14. ἡ ∠Ξ τῆι ΛΞ ABS, ἡ δζ τῇ λξ V2 Sca (voluerunt ἡ ∠Z τῇ ∠Ξ. corr. Bredow 15. 16. τῆς Β∠ πρὸς τὴν ∠Ζ] τῆς Ζ∠ πρὸς τὴν τρίτην ἀνάλογον τῶν)

ἀδύνατον (μείζων γὰρ ἡ Ε∠ τῆς ΔΖ)· οὐκ ἄρα ἡ ∠Μ τρίτη ἀνάλογόν ἐστιν τῶν Ε∠ ∠Ζ.

Εἰλήφθω τῶν Ε∠ ∠Ζ τρίτη ἀνάλογον ἡ ΟΠ. ἐπεὶ οὖν τῶν Ε∠ ∠Ζ τρίτη ἀνάλογόν ἐστιν ΟΠ, ἔστιν ὡς ἡ Ε∠ πρὸς τὴν ∠Ζ, οὕτως ἡ ∠Ζ πρὸς τὴν ΟΠ. καὶ ὡς ἄρα τὸ ἀπὸ τῆς ∠Ε πρὸς τὸ ἀπὸ τῆς ∠Ζ, οὕτως ἡ Ε∠ πρὸς τὴν ΟΠ. ἀλλʼ ἦν ὡς τὸ ἀπὸ τῆς Ε∠ πρὸς τὸ ἀπὸ τῆς ∠Ζ, οὕτως ἡ ∠Ζ πρὸς τὴν ∠Μ· διʼ ἴσου ἄρα ἐστὶν ὡς ἡ Ε∠ πρὸς τὴν ΟΠ, οὕτως ἡ Ζ∠ πρὸς τὴν ∠Μ· καὶ ἐναλλὰξ ἄρα ἐστὶν ὡς ἡ Ε∠ πρὸς τὴν ∠Ζ, οὕτως ἡ ΟΠ πρὸς τὴν ΔΜ. ἀλλʼ ἦν ὡς ἡ Ε∠ πρὸς τὴν ∠Z, οὕτως ἡ ∠Ζ πρὸς τὴν ΟΠ· καὶ ὡς ἄρα ἔ ∠Ζ πρὸς τὴν ΟΠ, οὕτως ἡ ΟΠ πρὸς τὴν ∠Μ· αἱ Ε∠ ∠Ζ ΟΠ ∠Μ ἄρα τέσσαρες οὖσαι ἐν τῇ συνεχεῖ καὶ ἐφεξῆς ἀναλογίᾳ εἰσί· τῶν Ε∠ ∠Μ ἄρα δύο μέσαι ἀνάλογόν εἰσιν αἱ ∠Ζ ΟΠ.