# De utilitate mathematicae 138

Theon Smyrnaeus, De utilitate mathematicae, Paragraph 138. Ancient Greek.

Canonical: https://interlinea.aeterna-institute.org/library/greek/theon-smyrnaeus/de-utilitate-mathematicae/138

γεωμετρικὴ δέ ἐστι μεσότης ἡ καὶ ἀναλογία κυρίως λεγομένη ἡ τῷ αὐτῷ λόγῳ ὑπερέχουσα καὶ ὑπερεχομένη, οἷον πολλαπλασίῳ ἢ ἐπιμορίῳ· οἷον αʹ βʹ δ΄. τά τε γὰρ δʹ τῶν βʹ διπλάσια καὶ τὰ βʹ τοῦ ἑνὸς διπλάσια· καὶ πάλιν ἡ ὑπεροχὴ τῶν βʹ ἐστὶ τὸ ἕν 〈καὶ ἡ ὑπεροχὴ τῶν δʹ τὰ βʹ〉, ταῦτα δὲ ὁμοίως ἐξεταζόμενά ἐστιν ἐν δι- πλασίῳ λόγῳ. συμβέβηκε δὲ ταύτῃ τῇ ἀναλογίᾳ τὸ ὑπὸ τῶν ἄκρων συντιθέμενον κατὰ πολλαπλασιασμὸν ἴσον εἶναι τῷ ἀπὸ τοῦ μέσου τετραγώνῳ. οἷον οἱ ἄκροι ἐπʼ ἀλλήλους πολλαπλασιαζόμενοι ποιοῦσι τὸν δʹ· ἅπαξ γὰρ δʹ δʹ· καὶ πάλιν ὁ βʹ ἐφʼ ἑαυτὸν λαμβανόμενος ποιεῖ τὸν δʹ δὶς γὰρ βʹ δ΄ ὥστε 〈τὸ〉 ὑπὸ τῶν ἄκρων ἴσον γίνεται τῷ ἀπὸ τοῦ μέσου· αʹ βʹ δʹ.

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Theon Smyrnaeus, De utilitate mathematicae, ed. Eduardus Hiller. Text: The Greek Library, from the Perseus Digital Library and other open sources, CC BY-SA 4.0. Changes: apostrophes normalised and the text divided into reading sections by Interlinea.
License: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/). Source: https://thegreeklibrary.pages.lisn.upsaclay.fr/works/tlg1724.tlg001.local001/.