Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 50
r AD. Then, the angle BAD will be a rightangle (Th. v. Cor), and therefore will bemeasured by half the semicircle AMD B(Bk. I, Th. i. Cor. 2). But the angle DA C being at the circumference, is measure 1by half the arc DC: hence,by the addition of equals, the twoangles BAD and DAC, or the entire… … 60 GEOMETRY Of the Circl THEOREM XV. If a tangent and a chord are parallel to each other, they willintercept equal arcs. Let the tangent ABC be parallel to thechord DF: then will the intercepted arcsDB, BF, be equal to each other. For, draw the chord DB. Then, sinceAC and DF are parallel, the angle…
Geometry · Plane 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-193-113.webp)
![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-24-10.webp)
