Re: [分析] METRIC SPACE

[suzzdicon (舒玆迪控)]

※ 引述《suzzdicon (舒玆迪控)》之銘言：
: Let X be a metric space,
: then X,ψ are open set.
: Why?

已知上述正確

=> X,ψ are open set
   _  __
=> X, ψ are closed set

=> ψ,X are open set

i.e.

X,ψ是開集亦為閉集?

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