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