Exercises on Euclid and in modern geometry for the use of schools, private students, and junior university students (1881)
McDowell, James L · Cambridge, Deighton, Bell, and Co. · leaf 91
(VI. D.). Let ABCD be any quadrilateral inscribed in a circle. 02 EXERCISES OX EUCLID [94. Make the angle ABE equal to CBE.BDC in the same segment BADC areequal (III. 21). Therefore the trianglesABE, CBD are equiangular, and thesides AB, AE correspond to BE, EC,therefore (79), AB. EC = AE . BE.… … AB . EC + CB . EA = AE. BE + CE. BE = AC . BE. q.e.d. 94. If perpendiculars be drawn from the extremities ofeach diagonal of any quadrilateral to the other diagonal, thesum of the perpendiculars on the first diagonal is to the sumof the jierpendiculars on the second diagonal as the seconddiagonal…
Geometry
Internet Archive · Wellesley College Library · 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-186-102.webp)