Chapter 11: Problem 4
Prove that \((0,1]=\bigcap_{n=1}^{\infty}(0,1+1 / n)\), as asserted in Example \(11.1 .6(\mathrm{a})\).
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Chapter 11: Problem 4
Prove that \((0,1]=\bigcap_{n=1}^{\infty}(0,1+1 / n)\), as asserted in Example \(11.1 .6(\mathrm{a})\).
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Let \(h: \mathbb{R} \rightarrow \mathbb{R}\) be defined by \(h(x):=1\) if \(0 \leq x \leq 1, h(x):=0\) otherwise. Find an open set \(G\) such that \(h^{-1}(G)\) is not open, and a closed set \(F\) such that \(h^{-1}(F)\) is not closed.
Find an infinite collection \(\left\\{K_{n}: n \in \mathbb{N}\right\\}\) of compact sets in \(\mathbb{R}\) such that the union \(\bigcup_{n=1}^{\infty} K_{n}\) is not compact.
Prove, using Definition \(11.2 .2\), that if \(K_{1}\) and \(K_{2}\) are compact sets in \(\mathbb{R}\), then their union \(K_{1} \cup K_{2}\) is compact.
Show that a set \(G \subseteq \mathbb{R}\) is open if and only if it does not contain any of its boundary points.
Show that \(A=\\{1 / n: n \in \mathbb{N}\\}\) is not a closed set, but that \(A \cup\\{0\\}\) is a closed set.
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