Bounded Below Real-Valued Function/Examples

Examples of Bounded Below Real-Valued Functions

$\tan x$ on $x \in \hointr 0 {\dfrac \pi 2}$

The real tangent function on the half-open interval $\hointr 0 {\dfrac \pi 2}$:

$\forall x \in \hointr 0 {\dfrac \pi 2}: \tan x$

is bounded below by $0$, but unbounded above.