Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 51
point E: then willthe angle AEC, or its equal DEB, bemeasured by half the sum of the inter-cepted arcs AC, DB. For, draw the chord AF parallel toCD. Then because of the parallels, theangle DEB will be equal to the angle FAB (Bk I. Th. xiv),and the arc FD to the arc AC. But the angle FAB is… … BOOK II. 51 Of the Circle. THEOREM XVII. The angle formed without a circle by the intersection cftwo secants is measured by half the difference of the interceptedarcs. Let the two secants DE and EB inter-sect each other at E: then will the angleDEB be measured by half the interceptedarcs CA and DB.…
Geometry · Plane trigonometry
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
![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-298-193.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-162-91.webp)
