# Scholia in Euclidis optica (scholia vetera) 19

Scholia in Euclidem, Scholia in Euclidis optica (scholia vetera), Section 19. Ancient Greek.

Canonical: https://interlinea.aeterna-institute.org/library/greek/scholia-in-euclidem/scholia-in-euclidis-optica-scholia-vetera/19

19. Πρὸς ὀρθὰς γωνίας ἴσαι p. 12, εἰ γάρ τις εἴποι, ὡς ἡ ΗΓ κάθετός ἐστι πρὸς τὴν Γ∠, ὡσαύτως δὲ καὶ ἡ ΖΒ πρὸς τὴν ΒΑ, δῆλον ἔσται τὸ ἄτοπον. εἰ γὰρ ἡ ὑπὸ ΗΓ∠ γωνία ὀρθή, καὶ ἡ ὑπὸ Β ὀρθὴ ἔσται.

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Scholia in Euclidem, Scholia in Euclidis optica (scholia vetera), ed. Johan Ludvig Heiberg, H. Menge. 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/tlg5022.tlg003.local001/.