/ ____\ / ____\
[0, pi - atan\\/ 15 /) U (pi + atan\\/ 15 /, 2*pi)
$$y\ in\ \left[0, - \operatorname{atan}{\left(\sqrt{15} \right)} + \pi\right) \cup \left(\operatorname{atan}{\left(\sqrt{15} \right)} + \pi, 2 \pi\right)$$
y in Union(Interval.Ropen(0, pi - atan(sqrt(15))), Interval.open(atan(sqrt(15)) + pi, 2*pi))
/ / / ____\\ / / ____\ \\
Or\And\0 <= t, t < pi - atan\\/ 15 //, And\t < 2*pi, pi + atan\\/ 15 / < t//
$$\left(0 \leq t \wedge t < - \operatorname{atan}{\left(\sqrt{15} \right)} + \pi\right) \vee \left(t < 2 \pi \wedge \operatorname{atan}{\left(\sqrt{15} \right)} + \pi < t\right)$$
((0 <= t)∧(t < pi - atan(sqrt(15))))∨((t < 2*pi)∧(pi + atan(sqrt(15)) < t))