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 164
gle. Therefore FE makes right angles with GH, that is, withany straight line drawn through E in the plane passing throughAB, CD. In like manner, it may be proved, that FE makes rightangles with every straight line which meets it in that plane. Buta straight line is at right angles to a plane when… … PROP. V. THEOR. If three straight hues meet all in one point, and astraight line stands at right angles to each of them inthat point; these three straight lines are in one and thesame plane.^ Let the straight line AB stand at right angles to each of thestraight lines BC, BD, BE, in B the point…
Mathematics, Greek · Geometry · Trigonometry
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