Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 45
x cot y — 1 r__, cot (x + y) = • [] v ^ J; coty+ cotx L J 56 PLANE TRIGONOMETRY SECTION XXIX FUNCTIONS OF THE DIFFERENCE OF TWO ANGLES In a unit circle (Fig. 52) let the angle AOB = x, COB = y;then the angle AOC — x — y. In order to express sin (x — y)and cos {x — y) in terms of thesines and… … CG CD Therefore,Again, OEODDGCD Therefore, = cos x; hence, CG — cos x x CD — cos x sin y. sin (x — y) = sin x cos y — cos x sin y. cos (x — y) = OF = OE + DG. —^ = cos x; hence, OE = cos ;c x 0D = cos ic cos y. [8] = sm# hence, DG = sin x x CD = sin x sin y. cos (x — y) = cos x cos y + sin x sin y.…
Trigonometry · Surveying · Navigation
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
