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 21
PROP. XI. PROB. To draw a straight line at right angles to a givenstraight line, from a given point in the same. Let AB be a given straight line, and C a point given in it: it isrequired to draw a straight line from the point C at right anglesto AB.* Take any point D in AC, and (3. 1.) make CE…
Mathematics, Greek · Geometry · Trigonometry
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.