Answer
$ a.\quad-\infty$.
$ b.\quad\infty$.
$ c.\quad-\infty$.
$ d.\quad\infty$.
Work Step by Step
See screenshot below.
$ a.\quad$
Nearing $x=\pi/2$ from the right, the graph falls without bound. $\displaystyle \lim_{x\rightarrow\pi/2^{+}}f(x)=-\infty$.
$ b.\quad$
Nearing $x=\pi/2$ from the left, the graph rises without bound. $\displaystyle \lim_{x\rightarrow\pi/2^{-}}f(x)=\infty$.
$ c.\quad$
Nearing $x=-\pi/2$ from the right, the graph falls without bound. $\displaystyle \lim_{x\rightarrow-\pi/2^{+}}f(x)=-\infty$.
$ d.\quad$
Nearing $x=-\pi/2$ from the left, the graph rises without bound. $\displaystyle \lim_{x\rightarrow-\pi/2^{-}}f(x)=\infty$.
