Real Analysis – Divergent Sequence in Compact Subset of R^n

analysisfunctional-analysisreal-analysis

Let $(x_n)$ be a divergent sequence in a compact subset of $\mathbb R^n$. Prove that there are two subsequences of $(x_n)$ that are convergent to different limit points.

Some ideas that might be helpful:

Heine-Borel theorem states that a subset of $\mathbb R^n$ is compact if and only if it is closed and bounded.

Bolzano-Weierstrass Theorem, every bounded sequence contains a convergent subsequence

A number $c$ is a limit point of $(x_n)$ if there exists a subsequence of $(x_n)$ convergening to $c$

Best Answer

By Bolzano Weierstrass you can pull out a convergent subsequence whose limit is some point $c$. Since your original sequence cannot converge, there's going to be a subsequence that doesn't converge to $c$. Now carefully pluck this subsequence so that it stays away at some fixed positive distance away from $c$. But this subsequence also satisfies Bolzano Weierstrass...

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