A treatise on special or elementary geometry (1877)
Olney, Edward, 1827-1887, Olney, Edward, 1827-1887. Elements of trigonometry, plane and spherical · New York : Sheldon · leaf 169
PROPOSITION IV. ^42, OrJieorem.—Two triangles, which have an angle in eachequal, and the sides about the equal a7iglesproportional, are similat. 148 ELEMENTAEY PLANE GEOMETRY. … Fig. 235. Dem.—In the triangles ABC and DEFlet C = F, and AC : DF :: CB : FE;then are the triangles similar. For, place F on its equal C, and let Dfall at D. Draw DE parallel to AB.Then AC : DC (= DF) :: BC : CE (337).But by hypothesis AC : DF :: BC : FE... CE = FE, and the triangles DCE andDFE are…
Geometry · Trigonometry
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