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 145
14^ ELEMENTS DE describe a circle meeting ABjpro-duced in G. And because AB isbisected in D, and produced to G,(6. 2.) AG.GB+DB==DG>=DE^ But (47. 1.) DE» = DB2+BE%therefore AG.GB -f DB^ = DB^ +BE» and AG.GB=BE. Now, BE=C; wherefore the straight line ABis produced to G, so that the rectan-gle… … Which was to PROP. XXX. PROB. To cut a given straight line in extreme and mean ratio. Let AB be the given straight line; it is required to cut it in ex-treme and mean ratio. Upon AB describe (46. 1.) the square BC, and produce CA to D,so that the rectangle CD.DA may be equal to the square UB…
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-65-42.webp)
