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 100
N any obtufe angledtriangle, thefquareof the fide fubtend-ing the obtufe angleexceeds the fiim of the fquaresof the fides containing the ob-tufe angle, by twice the rec-tangle contained by either ofthefe fides andthe produced partsof the fa?ne from the obtufeangle to the perpendicular letfall on it… … + by ^ + 2 • + By pr. 4, B. 2. ^ + > + 2 add ——— ^ to both 2 _ V (pr. 47, B. I.) + + • or ■; hence by 2 ^ (pr. 47, B. I.). Therefore, ^ • -■ + + Q. E. D. 68 BOOK II. PROP. XIII. THEOR. FIRST. SECOND.
Euclid's Elements · Geometry
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