Every bounded sequence is Cauchy?

7.9k Views Asked by At

I know that every Cauchy sequence is bounded, but is the reverse true?

1

There are 1 best solutions below

0
On BEST ANSWER

No. Consider the sequence $$1,-1,1,-1,1,-1,\dots$$ Clearly this seqeunce is bounded but it is not Cauchy. You can show this directly from the definition of Cauchy.

Alternatively, every Cauchy sequence (in $\mathbb{R}$) is convergent. Clearly the above sequence is not, thus it is not Cauchy.