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