Page 315 - Euclid's Elements of Geometry

ST EW iþ.

ELEMENTS BOOK 10

Δ ῥητὸν περιέχουσαι, καὶ ἡ Γ τῆς Δ μεῖζον δυνάται τῷ ἀπὸ C and D, so C (is) to D [Prop. 10.21 lem.]. And thus
συμμέτρου ἑαυτῇ μήκει. as A (is) to B, so C (is) to D. And A is commensurable
῾Ομοίως δὴ δειχθήσεται καὶ τῷ ἀπὸ ἀσυμμέτρου, ὅταν ἡ in square only with B. Thus, C (is) also commensurable
Α τῆς Β μεῖζον δύνηται τῷ ἀπὸ ἀσυμμέτρου ἑαυτῇ. in square only with D [Prop. 10.11]. And C is medial.
Thus, D (is) also medial [Prop. 10.23]. And since as A is
to B, (so) C (is) to D, and the square on A is greater than
(the square on) B by the (square) on (some straight-line)
commensurable (in length) with (A), the square on C is
thus also greater than (the square on) D by the (square)
on (some straight-line) commensurable (in length) with
(C) [Prop. 10.14].
Thus, two medial (straight-lines), C and D, commen-
surable in square only, (and) containing a rational (area),
have been found. And the square on C is greater than
(the square on) D by the (square) on (some straight-line)
commensurable in length with (C). †
So, similarly, (the proposition) can also be demon-
lbþ than (the square on B) by the (square) on (some
strated for (some straight-line) incommensurable (in
length with C), provided that the square on A is greater

straight-line) incommensurable (in length) with (A)
‡
[Prop. 10.30].
† C and D have lengths (1 − k ) and (1 − k ) times that of A, respectively, where k is defined in the footnote to Prop. 10.29.
2 3/4
2 1/4
‡ C and D would have lengths 1/(1 + k ) and 1/(1 + k ) times that of A, respectively, where k is defined in the footnote to Prop. 10.30.
2 3/4
2 1/4
Proposition 32
.
Εὑρεῖν δύο μέσας δυνάμει μόνον συμμέτρους μέσον To find two medial (straight-lines), commensurable in
περιεχούσας, ὥστε τὴν μείζονα τῆς ἐλάσσονος μεῖζον square only, (and) containing a medial (area), such that
δύνασθαι τῷ ἀπὸ συμμέτρου ἑαυτῇ. the square on the greater is larger than the (square on
the) lesser by the (square) on (some straight-line) com-
mensurable (in length) with the greater.
Α ∆ A D

Β Ε B E

Γ C
᾿Εκκείσθωσαν τρεῖς ῥηταὶ δυνάμει μόνον σύμμετροι αἱ Let three rational (straight-lines), A, B and C, com-
Α, Β, Γ, ὥστε τὴν Α τῆς Γ μεῖζον δύνασθαι τῷ ἀπὸ mensurable in square only, be laid out such that the
συμμέτρου ἑαυτῇ, καὶ τῷ μὲν ὑπὸ τῶν Α, Β ἴσον ἔστω τὸ square on A is greater than (the square on C) by the
ἀπὸ τὴς Δ. μέσον ἄρα τὸ ἀπὸ τῆς Δ· καὶ ἡ Δ ἄρα μέση (square) on (some straight-line) commensurable (in
ἐστίν. τῷ δὲ ὑπὸ τῶν Β, Γ ἴσον ἔστω τὸ ὑπὸ τῶν Δ, Ε. length) with (A) [Prop. 10.29]. And let the (square)
καὶ ἐπεί ἐστιν ὡς τὸ ὑπὸ τῶν Α, Β πρὸς τὸ ὑπὸ τῶν Β, Γ, on D be equal to the (rectangle contained) by A and B.
οὕτως ἡ Α πρὸς τὴν Γ, ἀλλὰ τῷ μὲν ὑπὸ τῶν Α, Β ἴσον Thus, the (square) on D (is) medial. Thus, D is also me-
ἐστὶ τὸ ἀπὸ τῆς Δ, τῷ δὲ ὑπὸ τῶν Β, Γ ἴσον τὸ ὑπὸ τῶν dial [Prop. 10.21]. And let the (rectangle contained) by
Δ, Ε, ἔστιν ἄρα ὡς ἡ Α πρὸς τὴν Γ, οὕτως τὸ ἀπὸ τῆς Δ D and E be equal to the (rectangle contained) by B and
πρὸς τὸ ὑπὸ τῶν Δ, Ε. ὡς δὲ τὸ ἀπὸ τῆς Δ πρὸς τὸ ὑπὸ C. And since as the (rectangle contained) by A and B
τῶν Δ, Ε, οὕτως ἡ Δ πρὸς τὴν Ε· καὶ ὡς ἄρα ἡ Α πρὸς τὴν is to the (rectangle contained) by B and C, so A (is) to
Γ, οὕτως ἡ Δ πρὸς τὴν Ε. σύμμετρος δὲ ἡ Α τῇ Γ δυνάμει C [Prop. 10.21 lem.], but the (square) on D is equal to
[μόνον]. σύμμετρος ἄρα καὶ ἡ Δ τῇ Ε δυνάμει μόνον. μέση the (rectangle contained) by A and B, and the (rectangle

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