Consider the function \(g: \mathbb{R} \backslash\\{0\\} \rightarrow \mathbb{R}\)
defined by \(g(x):=\cos (1 / x) .\) Prove the following:
(i) \(g\) is an even function.
(ii) \(\lim _{x \rightarrow 0} g(x)\) does not exist, but \(\lim _{x \rightarrow
0^{+}}[g(x)-g(-x)]\) exists. Also, \(g\)
cannot be extended to \(\mathbb{R}\) as a continuous function.
(iii) For any \(\delta>0, g\) is not uniformly continuous on \((0, \delta)\) as
well as on \((-\delta, 0)\), but it is uniformly continuous on \((\infty,-\delta]
\cup[\delta, \infty)\).
(iv) For any \(\delta>0, g\) is not monotonic, not convex, and not concave on
\((0, \delta)\) as well as on \((-\delta, 0)\).