Synagoge, Book 1 (2.14)

14 β. Ἔστω τις εὐθεῖα ἡ ΑΗ τετμημένη εἰς ἴσα κατὰ τὰ B Γ Ε Ζ· ὅτι ἐστὶν ὡς ἡ ΑΓ πρὸς ΓΒ, ἡ BΓ πρὸςτ
τὸ ἥμισυ τῆς ΒΓ, ὡς δὲ ἡ Α πρὸς Β. οὕτως ἡ Β πρὸς τὴν Γ καὶ τὸ τρίτον τῆς ΓΒ, ὡς δὲ ἡ ΑΕ πρὸς ΕΒ, οὕτως ἡ ΒΕ πρὸς τὴν ΕΓ καὶ τὸ τέταρτον τῆς ΓΒ, ὡς δὲ ἡ ΑΖ πρὸς τὴν ΖΒ, οὕτως ἡ ΒΖ πρὸς τὴν ΖΓ καὶ τὸ πέμπτον τῆς ΓΒ, ὡς δὲ ἡ ΑΗ πρὸς τὴν ΗΒ, οὕτως ἡ 8Η πρὸς
τὴν ΗΓ καὶ τὸ ἕκτον τῆς ΓΒ.

Ἔστι δὲ φανερὸν τῶν ἀριθμῶν παραληφθέντων ⋯ καὶ ἀεὶ οὕτως, ὅτι ὡς ὁ δοθεὶς τῶν ἴσων εὐθειῶν ἀριθμὸς ἀπὸ τοῦ Α πρὸς τὸν μονάδι ἐλάσσονα, οὕτως ὁ μονάδι ἐλάσσων πρὸς τὸν μονάδι αὐτοῦ ἐλάσσονα καὶ τῆς ΓΒ μόριον
ὁμώνυμον τῷ δοθέντι πλήθει τῶν ἴσων εὐθειῶν.