Elements of geometry and trigonometry. Revised and adapted to the course of mathematical instruction in the United States (1856)
Legendre, A. M. (Adrien Marie), 1752-1833, Davies, Charles, 1798-1876 · New York : A.S. Barnes · leaf 128
fijurth proportional to three given lines, A, B, C, Draw the two indefi-nite lines BE, BE, form-ing any angle with eachother. Upon BE takeBA^A, and BB=B;upon BE take BC=G,draw AC; ana throughthe point B, draw BX parallel to AC, and DX will bethe fourth proportional required. For, since BX is… … 124: GEOMETEY. Cor. A tliird proportional to two given lines, A, B, maybe found in the same manner, for it will be the same as afourth proportional to the three lines, J, i?, B. teoblem: III. To find a mean proportional heticeen iico given lines A and B, Upon the indefinite line DF^take J)E^A, and…
Geometry · Trigonometry
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