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 73
Drawand II (pr. 31.). I # (pr. 36.); and ■ i= twice ^^k ^^ = twice ^H (pr- 34-) i k (ax. 7.). Q^E. D. 40 BOOK I. PROP. XXXIX. THEOR,
Euclid's Elements · Geometry
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