An elementary treatise on geometry : simplified for beginners not versed in algebra (1833)
Grund, Francis J. (Francis Joseph), 1805-1863 · Boston : Carter, Hendee & Co. · leaf 77
of the triangle abc are in proportion to the three sides of the triangle ABC ; that is, let us have the proportions ac : ab = AC : AB ac : c6=AC : CB. Then make CD equal to ca, and draw through the point D the line DE, parallel to AB; and the triangle CDE will be similar to the triangle CAB (Query… … GEOMETRY. 73 paring these two proportions with the two precedingones, we shall have DC : DE = ac : abDC : CE = ac : cb(see theory of proportions, principle 3d). Now, as I have made DC equal to ac, I can write acinstead of DC, in the two last proportions; and they willthen become ac : DE = ac :…
Geometry, Plane
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