Page 425 - Euclid's Elements of Geometry

ST EW iaþ.

ELEMENTS BOOK 11

φέρεσθαι, τὸ περιληφθὲν σχῆμα. κἂν μὲν ἡ μένουσα 16. And the center of the sphere is the same as that of
εὐθεῖα ἴση ᾖ τῇ λοιπῇ [τῇ] περὶ τὴν ὀρθὴν περιφερομένῃ, the semicircle.
ὀρθογώνιος ἔσται ὁ κῶνος, ἐὰν δὲ ἐλάττων, ἀμβλυγώνιος, 17. And the diameter of the sphere is any straight-
ἐὰν δὲ μείζων, ὀξυγώνιος. line which is drawn through the center and terminated in
ιθʹ. ῎Αξων δὲ τοῦ κώνου ἐστὶν ἡ μένουσα εὐθεῖα, περὶ both directions by the surface of the sphere.
ἣν τὸ τρίγωνον στρέφεται. 18. A cone is the figure enclosed when, one of the
κʹ. Βάσις δὲ ὁ κύκλος ὁ ὑπὸ τῆς περιφερομένης εὐθείας sides of a right-angled triangle about the right-angle re-
γραφόμενος. maining (fixed), the triangle is carried around, and again
καʹ. Κύλινδρός ἐστιν, ὅταν ὀρθογωνίου παραλληλογράμ- established at the same (position) from which it began to
μου μενούσης μιᾶς πλευρᾶς τῶν περὶ τὴν ὀρθὴν γωνίαν πε- be moved. And if the fixed straight-line is equal to the re-
ριενεχθὲν τὸ παραλληλόγραμμον εἰς τὸ αὐτὸ πάλιν ἀποκα- maining (straight-line) about the right-angle, (which is)
τασταθῇ, ὅθεν ἤρξατο φέρεσθαι, τὸ περιληφθὲν σχῆμα. carried around, then the cone will be right-angled, and if
κβʹ. ῎Αξων δὲ τοῦ κυλίνδρου ἐστὶν ἡ μένουσα εὐθεῖα, less, obtuse-angled, and if greater, acute-angled.
περὶ ἣν τὸ παραλληλόγραμμον στρέφεται. 19. And the axis of the cone is the fixed straight-line
κγʹ. Βάσεις δὲ οἱ κύκλοι οἱ ὑπὸ τῶν ἀπεναντίον περια- about which the triangle is turned.
γομένων δύο πλευρῶν γραφόμενοι. 20. And the base (of the cone is) the circle described
κδʹ. ῞Ομοιοι κῶνοι καὶ κύλινδροί εἰσιν, ὧν οἵ τε ἄξονες by the (remaining) straight-line (about the right-angle
καὶ αἱ διάμετροι τῶν βάσεων ἀνάλογόν εἰσιν. which is) carried around (the axis).
κεʹ. Κύβος ἐστὶ σχῆμα στερεὸν ὑπὸ ἓξ τετραγώνων ἴσων 21. A cylinder is the figure enclosed when, one of
περιεχόμενον. the sides of a right-angled parallelogram about the right-
κϛʹ. ᾿Οκτάεδρόν ἐστὶ σχῆμα στερεὸν ὑπὸ ὀκτὼ τριγώνων angle remaining (fixed), the parallelogram is carried
ἴσων καὶ ἰσοπλεύρων περιεχόμενον. around, and again established at the same (position)
κζʹ. Εἰκοσάεδρόν ἐστι σχῆμα στερεὸν ὑπὸ εἴκοσι from which it began to be moved.
τριγώνων ἴσων καὶ ἰσοπλεύρων περιεχόμενον. 22. And the axis of the cylinder is the stationary
κηʹ. Δωδεκάεδρόν ἐστι σχῆμα στερεὸν ὑπὸ δώδεκα πεν- straight-line about which the parallelogram is turned.
ταγώνων ἴσων καὶ ἰσοπλεύρων καὶ ἰσογωνίων περιεχόμενον. 23. And the bases (of the cylinder are) the circles
described by the two opposite sides (which are) carried
around.
24. Similar cones and cylinders are those for which
the axes and the diameters of the bases are proportional.
aþ equal and equilateral triangles.
25. A cube is a solid figure contained by six equal
squares.
26. An octahedron is a solid figure contained by eight

27. An icosahedron is a solid figure contained by
twenty equal and equilateral triangles.
28. A dodecahedron is a solid figure contained by
twelve equal, equilateral, and equiangular pentagons.

Proposition 1
.
†
Εὐθείας γραμμῆς μέρος μέν τι οὐκ ἔστιν ἐν τῷ ὑπο- Some part of a straight-line cannot be in a reference
κειμένῳ ἐπιπέδῳ, μέρος δέ τι ἐν μετεωροτέρῳ. plane, and some part in a more elevated (plane).
Εἰ γὰρ δυνατόν, εὐθείας γραμμῆς τῆς ΑΒΓ μέρος μέν For, if possible, let some part, AB, of the straight-line
τι τὸ ΑΒ ἔστω ἐν τῷ ὑποκειμένῳ ἐπιπέδῳ, μέρος δέ τι τὸ ABC be in a reference plane, and some part, BC, in a
ΒΓ ἐν μετεωροτέρῳ. more elevated (plane).
῎Εσται δή τις τῇ ΑΒ συνvεχὴς εὐθεῖα ἐπ᾿ εὐθείας ἐν In the reference plane, there will be some straight-line
‡
τῷ ὑποκειμένῳ ἐπιπέδῳ. ἔστω ἡ ΒΔ· δύο ἄρα εὐθειῶν τῶν continuous with, and straight-on to, AB. Let it be BD.
ΑΒΓ, ΑΒΔ κοινὸν τμῆμά ἐστιν ἡ ΑΒ· ὅπερ ἐστὶν ἀδύνατον, Thus, AB is a common segment of the two (different)
ἐπειδήπερ ἐὰν κέντρῳ τῷ Β καὶ διαστήματι τῷ ΑΒ κύκλον straight-lines ABC and ABD. The very thing is impos-
γράψωμεν, αἱ διάμετροι ἀνίσους ἀπολήψονται τοῦ κύκλου sible, inasmuch as if we draw a circle with center B and

425