Elements of geometry : containing the first six books of Euclid, with a supplement on the quadrature of the circle, and the geometry of solids : to which are added, Elements of plane and spherical geometry (1826)
Playfair, John, 1748-1819, Euclid · Philadelphia : Marot & Walter · leaf 59
. 1.); therefore BC + AB =3BC.BD+AC; that is, AC is lessthan BC+AB by 2BC.BD. Secondly, Let AD fall without the triangle ABC*: Then becausethe angle atD is a right angle, the angle ACB is greater (16. 1.) thana right angle, and AB=(l2. 2.) AC+BC4-2BC.CD. Add BCto each; then AB-fBC=AC+2BC4-3BC.CD.… … OF GEOMETRY. BOOK II. 69 Lastly, Let the side AC be perpen*(Iicuiia.r to BC; (hen is BC the straightline between the perpendicular and theaeute angle ^.t B; and it is manifest that(47. 1.) AB=+BC^ = AC^-f2BC«=AC=+2BC.BC Therefore in every triangle,&e. Q,E.D.
Euclid's Elements · Geometry · Trigonometry
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