[分析] Cardinality、Compact

看板Math作者 (Q睿)時間14年前 (2011/10/03 21:58), 編輯推噓0(0011)
留言11則, 2人參與, 最新討論串1/3 (看更多)
1. Let A be the set of all functions from (0,1) to |R,and B be the set of all continuous funtions from (0,1) to |R. (a) Show that there is no 1-1 correspondence between |R and A. That is,|R and A do not have the same cardinlity. (b)Prove or disprove that there is a 1-1 correspondence between |R and B. 2.Let W be a compact subset of |R^n and {Va} be an open cover of W. Prove that there is an ε>0 such that for each subset E of W having diameter less than ε, there si a V in {Va} containing E. a0 1.(a)在拓樸課本的習題有看過 說#(A)= 2^(c) , c是|R的個數. 可是仍不知道怎麼證明,其他題則是無頭緒,希望版上得高手能給的指教 小弟感謝萬分! -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 1.175.134.40

10/04 05:01, , 1F
1(a)如果只要證題目說的用反證就好 假設有一一對應
10/04 05:01, 1F

10/04 05:01, , 2F
那麼可以構造出新函數blabla... 如果要證你說的就比
10/04 05:01, 2F

10/04 05:02, , 3F
較費工 (b)提示:給定連續函數在有理點上的值則此連續
10/04 05:02, 3F

10/04 05:03, , 4F
連續函數已被唯一決定
10/04 05:03, 4F

10/04 05:06, , 5F
2.從定義以及有限開集的交集是開集 不難吧
10/04 05:06, 5F

10/04 10:36, , 6F
我當初也有寫到第二題 我對題目的認知是說 他會在那
10/04 10:36, 6F

10/04 10:37, , 7F
堆covering裡面的其中一個 因為我當初想說用cpt
10/04 10:37, 7F

10/04 10:37, , 8F
找出有限個 但是選出來的那幾個可能沒有那個V_0
10/04 10:37, 8F

10/04 10:38, , 9F
也就是那個集合是否有可能落在取出來的finite cover
10/04 10:38, 9F

10/04 10:38, , 10F
中兩個的聯集
10/04 10:38, 10F

10/04 10:39, , 11F
(就是個交集一些,這種情況是不是又得縮小半徑?
10/04 10:39, 11F
文章代碼(AID): #1EYR-WAp (Math)
文章代碼(AID): #1EYR-WAp (Math)