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 167
is, we have only to provethe other, i. e., that the triangles are mu-tually equiangular. Make CD equal toFD,and draw DE parallel to AB. By thepreceding proposition CD (= FD): CA ::DE : AB. But, by hypotliesis, FD :CA :: DE : AB. Whence, DE = DE.In like manner CE : CB : : CD (=FD):CA. But, by… … Fig. 2.33. OF SIMILARITY. 147 the triangles ABC and DEF are mutually equiangular, and consequently similar. Q. E. D. 34:0, Sen.—As we now know that if two triangles are mutually equiangular,they are similar; or, if they have their sides proportional, they are similar, it willbe sufficient…
Geometry · Trigonometry
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