Jawabanmu

2014-05-18T16:42:50+07:00
cos 4x - cos 2x = -1
Cos 2(2x) - cos 2x + 1 = 0
2Cos²2x - 1 - Cos2x + 1 = 0

2Cos²2x - Cos2x = 0
Cos2x(2Cos2x - 1) = 0
Cos 2x = 0
       2x = 90' + k.360      dan      2x = 270' + k.360'
         x = 45' + k.180'                    x = 135' + k.180'
         x = 45' , 225'                        x = 135' , 315'

2Cos2x - 1 = 0
2Cos2x = 1
Cos2x = 1/2
       2x = 60' + k.360'        dan      2x = 300' + k.360'
         x = 30' + k . 180'                    x = 150' + k.180'
         x = 30' , 210'                          x = 150' , 330'
HP {30',45',135',150', 210',225',315',30'}