Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 49
uadrilateral, inscribed m a circle, be pro-duced out, the exterior angle will be equal to the inward oppositeangle Let the side BA, of the quadrilateralA BCD be produced to E, then will theoutward angle DAE be equal to the in-ward opposite angle C. For, the angle DAB plus the angle C,ts equal to… … THEOREM XIII. Two parallel chords intercept equal arcs. BOOK II. 49 Of the Circle Let the chords AB and CD be parallel:then will the arcs AC and BD be equal. For, draw the line AD. Then, becausethe lines AB and CD are parallel, thealternate angles ADC and DAB will beequal (Bk. I. Th. xii). But the…
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-43-22.webp)
