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 176
raw GH pa-rallel tO: AO; and make HF=tI A, joinFG; and when produced let it meetC A in D; join BD, BG, BF. BecauseGH is parallel to AD, and Fa=HA;therefore FG=GD, so that the line OFis bisected in G. And because BAO is.aright angle,BD=AB-f AO* (47.1.);and for the same reason^ BF^=AB^-|-AF^… … 176 SUPPLEMENT TO THE ELEMENTS 2AG34-2GF; and taking sGF from both, 3BG»=2AB=+2AG».or BG=>=AB3+AG; wherefore BAG (48.1.) is a right angle. NowAG is any straight line drawn in the plane of the lines AD, AF; andwhen a straight line is at right angles to any straight line which itmeets with.in a…
Euclid's Elements · Geometry · Trigonometry
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![An illustration from Nicolai Copernici Torinensis De reuolutionibus orbium coelestium, libri VI : Habes in hoc opere iam recens nato, & aedito, studiose lector, motus stellarum, tam fixarum, quàm erraticarum, cum ex ueteribus, tum etiam ex recentibus obseruationibus restitutos: & nouis insuper ac admirabilibus hypothesibus ornatos. Habes etiam tabulas expeditissimas, ex quibus eosdem ad quoduis tempus quàm facillime caculare poteris. Igitur eme, lege, fruere. [Line in Greek] (1543)](https://img.insideoutlibrary.com/img/200/ia-nicolaicopernici00cope-272-177.webp)
