Cos (x+30) - cos (x-30) = 1/2

jawab

cos (x+30) - cos (x - 30) = 1/2
- 2 sin 1/2 (x+30 + x - 30)  sin1/2 ( x+30 -x + 30)  =1/2
- 2 sin x sin 30 = 1/2
- 2 sin x (1/2) = 1/2
-2 sin x = 1
sin x = - 1/2 = - sin 30
sin x = sin(-30)
x = - 30 + n .360  atau x = (180)-(-30) + n. 360
x = - 30 + k. 360  atau x = 210  +n. 360
n = 0,1,2,3...
n =0 , x = - 30, x = 210
n = 1, x = 330, x = 560

x pada interval 0 < x < 360
x = (210 , 330)