/t\ sin|-| > -1/2 \2/
sin(t/2) > -1/2
7*pi 11*pi [0, ----) U (-----, 4*pi] 3 3
x in Union(Interval.Ropen(0, 7*pi/3), Interval.Lopen(11*pi/3, 4*pi))
/ / 7*pi\ / 11*pi \\ Or|And|0 <= t, t < ----|, And|t <= 4*pi, ----- < t|| \ \ 3 / \ 3 //
((0 <= t)∧(t < 7*pi/3))∨((t <= 4*pi)∧(11*pi/3 < t))