推 plover :No. 0 is not in A but 0 is a limit point of A. 03/28 02:00
→ inyu90313 :非常感謝~有豁然開朗的感覺~! 03/28 02:10
推 physicist512:基本上題目應該要說明metric是怎樣的距離函數... 03/28 09:13
→ physicist512:如果是...discrete metric,A且開且閉... 03/28 09:14
→ k6416337 :如果題目沒說 通常指的是|R跟norm metric 03/28 13:05