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 267
and .*. ^Hi^ = ^^ (B. 5. pr. 9). Q^E. D. H H 234 BOOK VI. PROP. XV. THEOR. … I. QUAL triangles, which haveone angle in each equal ( ^^ ^ ^B ), have the JiJts about the equal angles reciprocallyproportional
Euclid's Elements · Geometry
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