cos(t) > -1/2
2*pi 4*pi [0, ----) U (----, 2*pi] 3 3
t in Union(Interval.Ropen(0, 2*pi/3), Interval.Lopen(4*pi/3, 2*pi))
/ / 2*pi\ / 4*pi \\ Or|And|0 <= t, t < ----|, And|t <= 2*pi, ---- < t|| \ \ 3 / \ 3 //
((0 <= t)∧(t < 2*pi/3))∨((t <= 2*pi)∧(4*pi/3 < t))