/x\ 1 cot|-| >= ----- \2/ ___ \/ 3
cot(x/2) >= 1/(sqrt(3))
2*pi (0, ----] 3
x in Interval.Lopen(0, 2*pi/3)
/ 2*pi \ And|x <= ----, 0 < x| \ 3 /
(0 < x)∧(x <= 2*pi/3)