三角問題12-07-2013

6tan x = 5csc x
6sin x / cos x = 5 / sin x
6sin² x = 5cos x
6(1 - cos² x) = 5cos x
6cos² x + 5cos x - 6 = 0
(2cos x + 3) (3cos x - 2) = 0
cos x = - 3/2 (rejected)
or cos x = 2/3
x = 0.841 = 48.19° or x = 5.442 = 311.81°