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 429
NAPIERS RULES. 118, Hule !• ^rop*—In any right angled sjyJierical triangle^the sine of the middle part equals the pro-duct of the cosines of the opposite ex-j, tr ernes. Dem.—In the spliencal triangle BAC, rightangled at A, taking h, c, comp B, comp C, andcomp a in succession as middle paits, we… … sin h = cos (comp a) x cos (comp B), . or sin b = sin a sin B ; (1) sin c = cos (comp a) x cos (comp C), or sin c = sin a sin C ; (3) sin (comp B) = cos b x cos (comp C), or cos B = cos 6 sin C; (3) sin (comp C) = cos c x cos (comp B), or cos C = cos c sin B (4) sin (comp a) = cos b x cos c, or cos…
Geometry · Trigonometry
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