Cos x > 1/2 if and only if x belongs to one interval ]-pi/3,pi/3[ mod 2pi, according to the cosinus definition in the unitary circle. Also, such interval extremities would be written as -pi/3+2k.pi and pi/3+2l.pi, where k and l would be integers, in case not the entire ]-pi/3+2k.pi,pi/3+2k.pi[ would be inside the permissible interval [0,2016pi]. In fact, the last would contain the first when k in {1,2,3,...,1007} more than [0,pi/3[ (k=0) in one hand, and ]-pi/3+2016.pi,2016.pi] (l=1008) in the other hand.
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