New plane and spherical trigonometry, surveying, and navigation (1903)
Wentworth, G. A. (George Albert), 1835-1906 · Boston : Ginn & Company · leaf 96
° — cos-1x = 2 cos-:x,3cos-1x = 90°,cos-!x = 30°, 150°, or 270°,x = ±J V3, or 0. 14. Prove thattan (2 tan—xx) ; 2x1 -x2 Let tan— lx = y ;then x = tan ?/, tan (2 tan— lx) = tan 2 y2 tan ?/ 1 -tan2?/ 2x 1 -X2 15. Prove that sin (2Let tan- tan- -ix . zx; 1 +x2 = y\ then X = tan ?/, sin (2 tan~ ■!X) =… … If angle C is a right angle,a _ sin Ac sin C = sin ^4 sin B = sin B; — tan A;= c; sin B sin C 2. Prove by means of the Law ofSines that the bisector of an angleof a triangle divides the oppositeside into parts proportional to theadjacent sides. c sin C ab = sinsin AB a = c sin^l sin C b c 88 PLANE…
Trigonometry · Surveying · Navigation
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