概念---数学分析2：常用概念汇总(完备性，柯西序列等...)

完备性(Completeness)

Purpose:
它最初是用来表述，实数轴上没有洞，或者，没有间断点。
Cauchy completeness
Cauchy completeness is the statement that every Cauchy sequence of real numbers converges(From Wiki).

其中
Cauchy sequence
There is a sequence, $$x_1,x_2,x_3,...$$It is a Cauchy sequence if for every positive real number $\epsilon$, there is a positive integer $N$ such that for all natural numbers $m,n>N$, $$|x_m-x_n|<\epsilon$$

更多概念待更新~