DB45
2 cos 3x = - √3 cos 3x = - 1/2 √3 = - cos 30 = cos (180-30) = cos 150 3x = 150 + k. 360 atau 3x = - 150 + k. 360 x = 50 + k. 120 atau x = - 50 + k. 120 K = 0,1,2,3
k = 0 --> x = 50 , - 50 k = 1 --> x = 170, 70 k = 2 --> x = 290 , 190 k = 3 --> x = 410 , 310 untuk 0 < x < π---> 0 < x < 180° x = { 50, 70, 170) atau x = (5π/18 , 7π/18, 17π/18)
sehingga arc cos [] = 3x = 150 atau 210.
:.Jadi 3x = 150 U 3x = 210
:. HP = {x | x = 50 U x = 70}
cos 3x = - 1/2 √3 = - cos 30 = cos (180-30) = cos 150
3x = 150 + k. 360 atau 3x = - 150 + k. 360
x = 50 + k. 120 atau x = - 50 + k. 120
K = 0,1,2,3
k = 0 --> x = 50 , - 50
k = 1 --> x = 170, 70
k = 2 --> x = 290 , 190
k = 3 --> x = 410 , 310
untuk 0 < x < π---> 0 < x < 180°
x = { 50, 70, 170)
atau
x = (5π/18 , 7π/18, 17π/18)