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Consider a sequence $(x_n)$ in metric space $(X,d)$.

If the sequence of partial sums $\sum_{i=1}^n d(x_i,x_{i+1})$ of distances between consecutive terms converges in $\mathbb{R}$, then I understand why the sequence is Cauchy.

But is the converse statement true as well?

Mark
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1 Answers1

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No. A counterexample is afforded by the sequence $a_n=(-1)^n/n$ in $\mathbb R$ with the standard metric, which is Cauchy but for which the sum of distances is essentially twice the harmonic series and thus diverges.

joriki
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