Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 49
48 G E O M E T R Y . Of the Ci re! and the angle C is measured by half the arc DAB, which subtends it. Hence, the sum of the two angles, A and C is measured by half the entire circumference. I\ But half the entire circumference is the n measure of two%right angles; therefore, th? sum of the… … sum THEOREM XII. If the side of a quadrilateral, 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…
Geometry · Plane trigonometry
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
![An illustration from Vnderweysung der Messung : mit dem Zirkel vn[d] Richtscheyt in Linien, Ebnen vnnd gantzen Corporen (1525)](https://img.insideoutlibrary.com/img/200/ia-vnderweysungderm00drer-50-90.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-321-212.webp)