Jawabanmu

2013-12-05T20:03:52+07:00
Cos 2x + 7 sinx - 4 = 0
* cos 2x = 1 - 2sin^2 x
1 - 2sin^2 x + 7 sinx - 4 = 0
-2sin^2 x + 7 sin x - 3 = 0 (x -1)
2sin^2 x - 7 sin x + 3 = 0
(2 sinx - 1)(sin x - 3) = 0
2 sinx - 1 = 0          atau      sinx - 3 = 0
sinx = 1/2                           sinx = 3 (TIDAK MEMENUHI)
sinx = sin 30
     x = 30 + n.360 = 30
     x = (180 - 30) + n.360 = 150
jawaban : D

ini jawabanya : D. {60, 120} apa E. {30, 150} ?
Ohya, E :)