Jawabanmu

2014-05-20T12:44:21+07:00
1-2 sin^2 x - 5 cos x = 2
1 - 2(1-cos²x) - 5cosx = 2
1 - 2 + 2cos²x - 5cosx - 2 = 0
2cos²x -5cosx - 3 = 0
(2cosx+1)(cosx-3)= 0
2cosx + 1 = 0                atau  cosx - 3 = 0
2cosx = -1                              cosx = 3 tidak memenuhi
cosx = -1/2
     x = 120' , 240'
HP {120' , 240'}