求0°與360°之間所有滿足3cos x = 8 tan x

3cosx = 8tanx
3cosx = 8sinx/cosx
3cos²x - 8sinx = 0
3(1-sin²x) - 8sinx = 0
3 - 3sin²x - 8sinx = 0
3sin²x + 8sinx - 3 = 0
(3sinx - 1)(sinx + 3) = 0

sinx = 1/3 or sinx = -3 ( reject since -1<=sinx<=1 )

sinx = 1/3 ; x = 19.47⁰ ; 160.53⁰