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 430
s a right angle (Part II., 426), CE is perpendicular to OB (Part II.,S99), and DEC is equal to angle B of the triangle (Part II., 55S). CD = sin h, OD = cos b, CE = sin a, and OE — cos a. (1) From the triangle CDE, right angled at D, we have CD = CE X sin CED, or sin ft = sin a sin B. Generalized,… … Or (2) may be proved in the same manner as (1),by letting fall from B a perpendicular upon OA,from its foot drawing DE perpendicular to OC,and joining E and B. Then BD — sin c, OD =ccs c, BE = sin a, OE = cos a, and angle BED =angle C. From the triangle BDE,we have BD = BE X sin BED, or sin c = sin…
Geometry · Trigonometry
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