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 132
e triangles ABC, ADE about theequal angles are reciprocally proportional. But let the sides of the triangles ABC, ADE, about the equal an-gles be reciprocally proportional, viz. C A to AD, as EA to AB: thetriangle ABC is equal to the triangle ADE. Having joined BD as before; because CA : AD : ; EA… … I 433 l^LEMENTS the triangles ABC,EAD have the same ratio to the triangle BAD,wherefore the triangle ABC is equal (9. 5.) to the triangle EAD.Therefore equal triangles, ^c. Q. E. D. PROP. XVI. THEOR. If four straight lines be proportionals, the rectanglecontained by the extremes is equal to the…
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-67-45.webp)
