Schmall, Charles Nelson. [from old catalog] · New York, D. Van Nostrand company · leaf 179
an ellipse is constant and equal to 2 a. — In the figure of § 116, FP = e . PM = e . QN = e(0:^ + OQ) = e^^ + o^V .-. FP = a + ex. 162 ANALYTICAL GEOMETRY Also, FP = 6 . PM = e . QN = e . (OW - OQ). .-. rP = a- ex. .-. pr + PF=2a. Hence, the ellipse is the locus of a point which moves sothat the… … Bisect FF in 0, and take OA = 0A= a. Then A and Aare points on the curve. [Why ?] Now between F and Ftake any point K. With F as center and AK as radius,describe arcs; with F as center and AK as radius, describearcs intersecting the former in P and P^ By interchangingradii, Q and Q are found.…
Geometry, Analytic
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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-319-211.webp)
