The elements of Euclid : viz, the first six books, together with the eleventh and twelfth : the errors, by which Theon, or others, have long ago vitiated these books, are corrected, and some of Euclid's demonstrations are restored : also, The book of Euclid's data, in like manner corrected (1834)
Euclid, Euclid, Simson, Robert, 1687-1768 · Philadelphia : Desilver & Thomas · leaf 60
PROP. IIL THEOR. If a straight line drawn through the centre of a cir-cle bisect a straight line in it which does not passthrough the centre, it shall cut it at right angles, and,if it cuts it at right angles, it shall bisect it. Let ABC be a circle; and let CD, a straight line drawn through BOOK… … the centre, bisect any straight line AB, which does not passthrough the centre, in the point F: it cuts it also at right angles. Take (1.3.) E the centre of the circle, and join EA, EB. Then,because AF is equal to FB, and FE common to the two trianglesAFE, BFE, there are two sides in the one equal…
Mathematics, Greek · Geometry · Trigonometry
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