Find four smallest positive numbers theta such that cosine = 1/2

Cos (x) = 0.5

x=pi/3

since cos is postive in the fourth quadrant and first quadrant

x=pi/3+2*pi*k where k is an integer

fourth quadrant

x = (-pi/3) + 2*pi*k where k is an integer

the first 3 values of K in the first quadrant are

pi/3,7*pi/3,13*pi/3

the first three postive values for the fourth quadrant are

5*pi/3,11*pi/3,19*pi/3

so the smallest three are

pi/3,5*pi/3,7*pi/3,11*pi/3