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