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 131
E (2. 6.), becauseAD is parallel to EC; therefore BA is to AC, as BA to AE (II.5.): consequently AC is equal to AE (9. 5.), and the angle AECis therefore equal to the angle ACE (5. 1.): but the angle AECis equal to the outward and opposite angle BAD: and the angleACE is equal to the alternate angle… … BOOK VI. THE ELEMENTS OF EUCLID. 129 PROP. A. THEOR. If the outward angle of a triangle made by producingone of its sides, be divided into two equal angles, by astraight line which also cuts the base produced; thesegments between the dividing line and the extremitiesof the base have the same ratio…
Mathematics, Greek · Geometry · Trigonometry
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