Def 14.1 (𝑥{𝑛}) is called Cauchy if (∀𝜀>0)(∃𝑛0)(∀𝑛,𝑚>𝑛0)𝑑(𝑥𝑛,𝑥𝑚)<𝜀 Thm All convergent sequence in complete Metric Space is Cauchy sequence.