2 cos X 1 0 pi6 2n pi 5 pi6 2n pi pi3 2n pi 5 pi3 2n p

2 cos X - 1 = 0 pi/6 + 2n pi: 5 pi/6 + 2n pi pi/3 + 2n pi: 5 pi/3 + 2n pi pi/4 + 2n pi: 5 pi/4 + 2n pi 2 pi/3 + 2n pi: 4 pi/3 + 2n pi

Solution

2 cosx - 1 = 0

adding 1 on both sides

2 cos x = 1

dividing both sides by 2

cos x = 1/2

x = cos ^-1 ( 1/2 )

x = pi/3 + 2pi*n , 5pi/3 + 2pi*n

option b is correct