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 66
oppofte angles ( aiid ^^^), and the three internal angles ofevery triangle taken together areequal to two right angles. … Through the point / draw II (pr. 3i-)- Then
Euclid's Elements · Geometry
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