Act.trig.02 sin theta >= 1

[karush]

For $-\dfrac{\pi}{2}\le \theta \le \dfrac{\pi}{2}
\quad |\sin{\theta}\ge 1|$ is true for all and only the values of $\theta$ in which of the following sets
$a.\ \left\{-\dfrac{\pi}{2},\dfrac{\pi}{2}\right\}
\quad b.\ \left\{\dfrac{\pi}{2}\right\}
\quad c.\ \left\{\theta | -\dfrac{\pi}{2}< \theta < \dfrac{\pi}{2}\right\}
\quad d.\ \left\{\theta | -\dfrac{\pi}{2}\le \theta < \dfrac{\pi}{2} \le \right\}
\quad e.\ \textit{empty set}$

I chose b since $\sin\theta$ can only be 1 at $\dfrac{\pi}{2}$

I have seen a lot of students miss this one
not sure why

what is the symbol for an empty set? or better yet the latex code