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 203
r, revolving S-ahc as be-fore till the facial angle aSc falls in its equal (?) ASC, since the diedral B-SC-A= B-SA-C (by hypothesis) and the latter equals its opposite h-Sa-c, the plane hSawill fall in the plane BSC ; and, for like reasons, the plane hSc will fall in BSA.Now, as these planes… … PROPOSITION X. —Two symmetrical triedrals are equivalent. Dem.—S-ABC is equivalent to its symmetrical triedral S-dbc. For, let dD be so drawn that the angles DSA,DSC, and DSB shall be equal, and consequently dSa= dSc = dSb, and the latter respectively equal to theformer. Then the isosceles •…
Geometry · Trigonometry
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