ια.

Ἐὰν μέγεθος μεγέθους δοθέντι μεῖζον ᾖ ἢ ἐν λόγῳ, τὸ αὐτὸ καὶ συναμφοτέρου δοθέντι μεῖζον ἔσται ἢ ἐν λόγῳ, καὶ ἐὰν τὸ αὐτὸ συναμφοτέρου δοθέντι μεῖζον ᾖ ἢ ἐν λόγῳ, τὸ αὐτὸ καὶ τοῦ λοιποῦ δοθέντι μεῖζον ἔσται ἢ ἐν λόγῳ. μέγεθος γὰρ τὸ ΑΒ τοῦ ΒΓ δοθέντι μεῖζον ἔστω ἢ ἐν λόγῳ· λέγω, ὅτι καὶ τοῦ ΑΓ δοθέντι μεῖζόν ἐστιν ἢ ἐν λόγῳ. ἐπεὶ γὰρ τὸ ΑΒ τοῦ ΒΓ δοθέντι μεῖζόν ἐστιν ἢ ἐν λόγῳ, ἀφῃρήσθω τὸ δοθὲν μέγεθος τὸ ΑΔ· λοιποῦ ἄρα τοῦ ΔΒ πρὸς τὸ ΒΓ λόγος ἐστὶ δοθείς. ἀνάπαλιν καὶ συνθέντι λόγος ἐστὶ τοῦ ΓΔ πρὸς τὸ ΔΒ δοθείς· ὁ αὐτὸς αὐτῷ γεγονέτω ὁ τοῦ ΑΔ πρὸς τὸ ΔΕ· λόγος ἄρα καὶ τοῦ ΑΔ πρὸς τὸ ΔΕ δοθείς· δοθὲν δὲ τὸ ΑΔ· δοθὲν ἄρα καὶ τὸ ΔΕ· ὥστε καὶ λοιπὸν τὸ ΕΑ δοθέν ἐστιν. ἔστι δὲ καὶ ὅλου τοῦ ΑΓ πρὸς ὄλον τὸ ΕΒ λόγος δοθείς· ὥστε καὶ τοῦ ΕΒ πρὸς ΑΓ λόγος ἐστὶ δοθείς. καί ἐστι δοθὲν τὸ ΑΕ· τὸ ΒΑ ἄρα τοῦ ΑΓ δοθέντι μεῖζόν ἐστιν ἢ ἐν λόγῳ. ἀλλὰ δὴ τὸ ΒΑ συναμφοτέρου τοῦ ΑΓ δοθέντι μεῖζον ἔστω ἢ ἐν λόγῳ· λέγω, ὅτι τὸ αὐτὸ τὸ ΑΒ καὶ τοῦ λοιποῦ τοῦ ΒΓ δοθέντι μεῖζον ἔσται ἢ ἐν λόγῳ. ἐπεὶ γὰρ τὸ ΑΒ τοῦ ΑΓ δοθέντι μεῖζόν ἐστιν ἢ ἐν λόγῳ, ἀφῃρήσθω τὸ δοθὲν μεγεθος τὸ ΑΕ· λοιποῦ ἄρα τοῦ ΕΒ πρὸς τὸ ΑΓ λόγος ἐστὶ δοθείς· ὥστε καὶ τοῦ ΑΓ πρὸς τὸ ΕΒ λόγος ἐστὶ δοθείς· ὁ αὐτὸς αὐτῷ γεγονέτω ὁ τοῦ ΑΔ πρὸς ΕΔ· καὶ τοῦ ΔΑ ἄρα πρὸς ΕΔ λόγος ἐστὶ δοθείς· καὶ ἀναστρέψαντι τοῦ ΔΑ πρὸς ΑΕ λόγος δοθείς· καὶ ἀνάπαλιν τοῦ ΕΑ πρὸς τὸ ΑΔ λόγος ἐστὶ δοθείς. καὶ δοθὲν τὸ ΑΕ· δοθὲν ἄρα καὶ ὅλον τὸ ΑΔ. καὶ ἐπεὶ ὅλου τοῦ ΑΓ πρὸς ὅλον τὸ ΕΒ λόγος ἐστὶ δοθείς, ὧν τοῦ ΑΔ πρὸς τὸ ΔΕ λόγος ἐστὶ δοθείς, ἔσται καὶ λοιποῦ τοῦ ΓΔ πρὸς λοιπὸν τὸ ΔΒ λόγος δοθείς· καὶ διελόντι τοῦ ΓΒ πρὸς τὸ ΔΒ λόγος ἐστὶ δοθείς· ὥστε καὶ τοῦ ΔΒ πρὸς τὸ ΒΓ λόγος ἐστὶ δοθείς. καί ἐστι δοθὲν τὸ ΔΑ· τὸ ΑΒ ἄρα τοῦ ΒΓ δοθέντι μεῖζόν ἐστιν ἢ ἐν λόγῳ.