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 38
BOOK I. PROP. V. THEOR. N anj ifofceles triangle A if the equal Jidesbe produced, the externalangles at the bafe are equal, and theinternal angles at the bafe are alfoequal. Produce and y (poft. 2.), take — - = 9 (pr- 3-); draw -i^——» and n . … Then in both, and A A / \ and / \ we have, = (conft.), A common to (hyp.) /. Jk =and ^ = ^ (pr. 4.).
Euclid's Elements · Geometry
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