{"id":1466,"date":"2017-11-14T23:12:08","date_gmt":"2017-11-15T04:12:08","guid":{"rendered":"http:\/\/blog.richmond.edu\/math320\/?p=1466"},"modified":"2017-11-14T23:12:08","modified_gmt":"2017-11-15T04:12:08","slug":"muddiest-point-1114","status":"publish","type":"post","link":"https:\/\/blog.richmond.edu\/math320\/2017\/11\/14\/muddiest-point-1114\/","title":{"rendered":"Muddiest Point 11\/14"},"content":{"rendered":"<p>For me, the muddiest point of this lecture was understanding the order of choosing <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=N&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"N\" class=\"latex\" \/> and <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/>. I will illustrate this in the proof of Theorem 6.2.6.<\/p>\n<p>Statement of Proof: If <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f_n+%5Cto+f&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f_n &#92;to f\" class=\"latex\" \/> uniformly on <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"A\" class=\"latex\" \/> and <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f_n&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f_n\" class=\"latex\" \/> continuous on <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"A\" class=\"latex\" \/> for all <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=n&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"n\" class=\"latex\" \/>, then\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f\" class=\"latex\" \/> is continuous on\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"A\" class=\"latex\" \/> as well.<\/p>\n<p>Proof: Let\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cepsilon+%3E0&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;epsilon &gt;0\" class=\"latex\" \/>. Choose\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=N&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"N\" class=\"latex\" \/> such that\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%7C%7Cf_N-f%7C%7C_%7B%5Cinfty%2CA%7D+%3C+%5Cfrac%7B%5Cepsilon%7D%7B3%7D&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"||f_N-f||_{&#92;infty,A} &lt; &#92;frac{&#92;epsilon}{3}\" class=\"latex\" \/>. Choose\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> such that\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%7Cx-c%7C+%3C+%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"|x-c| &lt; &#92;delta\" class=\"latex\" \/> implies\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%7Cf_N%28x%29-f_N%28c%29%7C+%3C+%5Cfrac%7B%5Cepsilon%7D%7B3%7D.&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"|f_N(x)-f_N(c)| &lt; &#92;frac{&#92;epsilon}{3}.\" class=\"latex\" \/>. By the triangle inequality,\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%7Cf%28x%29-f%28c%29%7C+%5Cleq+%7Cf%28x%29-f_N%28x%29%7C%2B%7Cf_n%28x%29-f_n%28c%29%7C%2B%7Cf_n%28c%29-f%28c%29%7C+%3C+3+%28%5Cfrac%7B%5Cepsilon%7D%7B3%7D%29%3D+%5Cepsilon&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"|f(x)-f(c)| &#92;leq |f(x)-f_N(x)|+|f_n(x)-f_n(c)|+|f_n(c)-f(c)| &lt; 3 (&#92;frac{&#92;epsilon}{3})= &#92;epsilon\" class=\"latex\" \/>.<\/p>\n<p>It is necessary to choose\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=N&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"N\" class=\"latex\" \/> before\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> because\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> relies on\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=N&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"N\" class=\"latex\" \/>. Imagine trying to choose\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> first. You wouldn&#8217;t be able to choose a\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> that would help solve the problem because the correct <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta\" class=\"latex\" \/> relies on\u00a0<img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=N&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"N\" class=\"latex\" \/>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>For me, the muddiest point of this lecture was understanding the order of choosing and . I will illustrate this in the proof of Theorem 6.2.6. Statement of Proof: If uniformly on and continuous on for all , then\u00a0 is continuous on\u00a0 as well. Proof: Let\u00a0. Choose\u00a0 such that\u00a0. Choose\u00a0 such that\u00a0 implies\u00a0. By the [&hellip;]<\/p>\n","protected":false},"author":3530,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[58820,58822],"tags":[],"class_list":["post-1466","post","type-post","status-publish","format-standard","hentry","category-daily-blogs","category-muddiest-point"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7L4E1-nE","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/posts\/1466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/users\/3530"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/comments?post=1466"}],"version-history":[{"count":0,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/posts\/1466\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/media?parent=1466"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/categories?post=1466"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/tags?post=1466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}