{"id":415,"date":"2014-06-23T11:51:22","date_gmt":"2014-06-23T18:51:22","guid":{"rendered":"http:\/\/www.bellevuecollege.edu\/math\/?page_id=415"},"modified":"2022-02-07T15:40:58","modified_gmt":"2022-02-07T23:40:58","slug":"diag","status":"publish","type":"page","link":"https:\/\/www.bellevuecollege.edu\/math\/links\/mathsnips\/infinity\/diag\/","title":{"rendered":"Cantor&#8217;s Diagonalization Argument"},"content":{"rendered":"\n<p>Suppose that the infinity of decimal numbers between zero and one is the same as the infinity of counting numbers. Then all the decimal numbers can be denumerated in a list.<\/p>\n\n\n\n<p>1 \u2192 d<sub>1<\/sub> = 0.d<sub>11<\/sub>d<sub>12<\/sub>d<sub>13<\/sub>d<sub>14<\/sub> &#8230;&#8230;.<br>2 \u2192 d<sub>2<\/sub> = 0.d<sub>21<\/sub>d<sub>22<\/sub>d<sub>23<\/sub>d<sub>24<\/sub> &#8230;&#8230;.<\/p>\n\n\n\n<p>3 \u2192 d<sub>3<\/sub> = 0.d<sub>31<\/sub>d<sub>32<\/sub>d<sub>33<\/sub>d<sub>34<\/sub> &#8230;&#8230;.<\/p>\n\n\n\n<p>4 \u2192 d<sub>4<\/sub> = 0.d<sub>41<\/sub>d<sub>42<\/sub>d<sub>43<\/sub>d<sub>44<\/sub> &#8230;&#8230;.<\/p>\n\n\n\n<p><strong>.<\/strong><br><strong>.<\/strong><br><strong>.<\/strong><br>n \u2192 d<sub>n<\/sub> = 0.d<sub>n1<\/sub>d<sub>n2<\/sub>d<sub>n3<\/sub>d<sub>n4<\/sub> &#8230;&#8230;.<br><strong>.<\/strong><br><strong>.<\/strong><br><strong>.<\/strong><br>Consider the decimal number x = 0.x<sub>1<\/sub>x<sub>2<\/sub>x<sub>3<\/sub>x<sub>4<\/sub>x<sub>5<\/sub> &#8230;&#8230;. , where x<sub>1<\/sub> is any digit other than d<sub>11<\/sub>; x<sub>2<\/sub> is different from d<sub>22<\/sub>; x<sub>3<\/sub> is not equal to d<sub>33<\/sub>; x<sub>4<\/sub> is not d<sub>44<\/sub>; and so on. Now, x is a decimal number, and x is less than one, so it must be in our list. But where? x can&#8217;t be first, since x&#8217;s first digit differs from d<sub>1<\/sub>&#8216;s first digit. x can&#8217;t be second in the list, because x and d<sub>2<\/sub> have different hundredths place digits. In general, x is not equal to d<sub>n<\/sub>, since their nth digits are not the same.<br>x is nowhere to be found in the list. In other words, we have exhibited a decimal number that ought to be in the list but isn&#8217;t. No matter how we try to list the decimal numbers, at least one will be left out. Therefore, &#8220;listing&#8221; the decimal numbers is impossible, so <strong>the infinity of decimal numbers is greater than the infinity of counting numbers.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Suppose that the infinity of decimal numbers between zero and one is the same as the infinity of counting numbers. Then all the decimal numbers can be denumerated in a list. 1 \u2192 d1 = 0.d11d12d13d14 .......2 \u2192 d2 = 0.d21d22d23d24 ....... 3 \u2192 d3 = 0.d31d32d33d34 ....... 4 \u2192 d4 = 0.d41d42d43d44 ....... ...n <a class=\"read-more\" href=\"https:\/\/www.bellevuecollege.edu\/math\/links\/mathsnips\/infinity\/diag\/\">...more about Cantor&#8217;s Diagonalization Argument<\/a><\/p>\n","protected":false},"author":115,"featured_media":0,"parent":124,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"class_list":["post-415","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/pages\/415","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/users\/115"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/comments?post=415"}],"version-history":[{"count":3,"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/pages\/415\/revisions"}],"predecessor-version":[{"id":2113,"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/pages\/415\/revisions\/2113"}],"up":[{"embeddable":true,"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/pages\/124"}],"wp:attachment":[{"href":"https:\/\/www.bellevuecollege.edu\/math\/wp-json\/wp\/v2\/media?parent=415"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}