Sequence

Cauchy sequence

A sequence over a metric space (𝑋,𝑑) is said to be Cauchy iff its terms get arbitrarily close together. More formally, a sequence (𝑎𝑛)𝑛=1 is a Cauchy sequence iff. for every 𝜖 >0 there exists an integer 𝑁 such that 𝑑(𝑎𝑚,𝑎𝑛) <𝜖 for any 𝑚 >𝑛 >𝑁. #m/def/anal

It is easy to prove that every convergent sequence is a Cauchy sequence using the triangle inequality. A metric space in which every convergent sequence is a Cauchy sequence is called a Complete metric space.


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