Elements of geometry : containing the first six books of Euclid, with a supplement on the quadrature of the circle, and the geometry of solids : to which are added, Elements of plane and spherical geometry (1826)
Playfair, John, 1748-1819, Euclid · Philadelphia : Marot & Walter · leaf 136
therefore has to BG theduplicate ratio of that which BC has to EF. But as BC to BG, sois(l. 6.) the triangle ABC to the triangle ABG: therefore the triangleABC has to the triangle ABG the duplicate ratio of that which BChas to EF: and the triangle ABG is equal to the triangle DEF; where-fore also… … 136 ELEMENTS portionals, as the first is to the third, so is any triangle upon the firstto a similar, and similarly described triangle upon the second. PROP. XX. THEOR. Similar polygons may be divided into the same numberof similar triangles, having the same ratio to one anotherthat the polygons…
Euclid's Elements · Geometry · Trigonometry
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