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 168
h of them equal and parallel toBE. But straight lines that are parallel tothe same straight line, and not in the sameplane with it, are parallel (9. 11.) to oneanother. Therefore AD is parallel to CF;and it is equal (1. Ax. 1.) to it, and AC,DF join them towards the same parts; andtherefore (33.… … PROP. XI. PROB. To draw a straight line perpendicular to a plane^from a given point above it. Let A be the given point above the plane BH; it is requiredto draw from the point A a straight line perpendicular to theplane BH. In the plane draw any straight line BC, and from the point Adraw (12. 1.)…
Mathematics, Greek · Geometry · Trigonometry
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