Newton's principia, first book sections I, II, III, with notes and illustrations and a collection of problems, principally intended as examples of Newton's methods (1900)
f the force tend to the centre of tlie elliptic orbit describedhy a hody^ th^ time between the extrernities of conjugate diametersvoill he -constariL For the area PCD is constant, (8) The velocity at any point of an ellipse about a force tend-ing to a focus is compounded of two uniform velocities,… … 148 NEWTON. CH are perpendicular to the three du-ections; therefore thevelocity represented by HZ in magnitude is the resultant ofthe two represented by GZ and HC] but the velocity perpen-dicular to HZ= -QY~ 1? --^^5 therefore the velocities perpen-dicular to HC and CZ are f^ ae and ,-^ a. XVIII.…
Mechanics · Celestial mechanics
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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-61-37.webp)
