The first six books of the elements of Euclid, in which coloured diagrams and symbols are used instead of letters for the greater ease of learners (1847)
Byrne, Oliver, Whittingham, Charles, 1795-1876, Chiswick Press · London : William Pickering · leaf 135
(B. 3.pr. i8.) .. ^^ =: I Ji, a right angle ; but ffj^ = I 1 (hyp.) and /. ^ = a part equal to the whole, which is abfurd. Therefore the affumed point is not the centre; and inthe fame manner it can be demonftrated, that no otherpoint without _„_^ is the centre. Q. E. D. 102 BOOK III. PROP. XX.… … HE angle at the centre of a circle, is doublethe angle at the circumference, when theyhave the fame part of the circumference fortheir bafe. FIGURE I.Let the centre of the circle be on a fide of ^ , Becaufe i = ^ = ^ (B. i.pr.5.). But
Euclid's Elements · Geometry
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