{"id":1218,"date":"2017-10-22T17:54:53","date_gmt":"2017-10-22T21:54:53","guid":{"rendered":"http:\/\/blog.richmond.edu\/math320\/?p=1218"},"modified":"2017-10-22T17:58:52","modified_gmt":"2017-10-22T21:58:52","slug":"what-happened-1019","status":"publish","type":"post","link":"https:\/\/blog.richmond.edu\/math320\/2017\/10\/22\/what-happened-1019\/","title":{"rendered":"What Happened 10\/19"},"content":{"rendered":"<p class=\"p1\">On Thursday 10\/19, we began class with a weekly situation, &#8220;Are we doing mathematics or philosophy?&#8221;. Dr. LeCrone then read a thorough and quite verbose definition of a function from another analysis book. We then switched to the topic of the day: continuity, part of Ch. 4 (Continuity on Compact Sets and Uniform Continuity).<\/p>\n<p class=\"p1\">We learned the definition of uniform continuity and point-wise continuity. We then looked at three example functions, <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f%28x%29%3D+2x%2C+g%28x%29%3Dx%5E2%2C+h%28x%29%3D%5Csqrt%28x%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f(x)= 2x, g(x)=x^2, h(x)=&#92;sqrt(x)\" class=\"latex\" \/> all with <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=A%3D%5B0%2C%5Cinfty%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"A=[0,&#92;infty)\" class=\"latex\" \/>, and examined their graphs, specifically examining <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=V_%7B%5Cdelta_1%7D+%28c_1%29%2C+V_%7B%5Cdelta_2%7D+%28c_2%29%2C+V_%7B%5Cdelta_3%7D+%28c_3%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"V_{&#92;delta_1} (c_1), V_{&#92;delta_2} (c_2), V_{&#92;delta_3} (c_3)\" class=\"latex\" \/> and <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=V_%7B%5Cepsilon_1%7D+%28f%28c_1%29%29%2C+V_%7B%5Cepsilon_2%7D+%28f%28c_2%29%29%2C+V_%7B%5Cepsilon_3%7D+%28f%28c_3%29%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"V_{&#92;epsilon_1} (f(c_1)), V_{&#92;epsilon_2} (f(c_2)), V_{&#92;epsilon_3} (f(c_3))\" class=\"latex\" \/>. Through this, we were able to visually apply our definition of uniform continuity and check whether each met the definition.<\/p>\n<p class=\"p1\">Dr. LeCrone then gave a proof template, and we completed the proof for proving <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f%28x%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f(x)\" class=\"latex\" \/> was continuous on the domain.<\/p>\n<p class=\"p1\">Proof template: let <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\" \/> &#8230; (details regarding <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\" \/>) &#8230; choose <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta%3D&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta=\" class=\"latex\" \/> ____ , depending only on <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cepsilon&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;epsilon\" class=\"latex\" \/>. Let <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=c+%5Cin+A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"c &#92;in A\" class=\"latex\" \/> be arbitrary and consider <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=x+%5Cin+A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"x &#92;in A\" class=\"latex\" \/> with <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\" \/> &#8230; (details).. Thus, <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%7Cf%28x%29-f%28c%29%7C%3C+%5Cepsilon&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"|f(x)-f(c)|&lt; &#92;epsilon\" class=\"latex\" \/>. Since <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=c&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"c\" class=\"latex\" \/> was arbitrary, we have unif. continuity of <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\" \/> on domain <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\" \/>.<\/p>\n<p class=\"p1\">We then completed this proof, using <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cdelta%3D+%5Cepsilon%2F2&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;delta= &#92;epsilon\/2\" class=\"latex\" \/><\/p>\n<p class=\"p1\">We then constructed a Sequential Criteria for Uniform Continuity and and a Sequential Characterization.<\/p>\n<p class=\"p1\">We used this sequential characterization, choosing <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%28x_n%29%3D%28n%29%2C+%28y_n%29%3D%28n-%5Cfrac%7B1%7D%7Bn%7D%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"(x_n)=(n), (y_n)=(n-&#92;frac{1}{n})\" class=\"latex\" \/>, and <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=%5Cepsilon_0%3D1&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"&#92;epsilon_0=1\" class=\"latex\" \/> to show that <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=g%28x%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"g(x)\" class=\"latex\" \/> is not uniformly continuous.<\/p>\n<p class=\"p1\">We observed that <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=h%28x%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"h(x)\" class=\"latex\" \/> requires us to split the domain in order to characterize, which we will cover on Tuesday.<\/p>\n<p class=\"p1\">Finally we covered two theorems. Theorem 4.4.1 states that If $latex\u00a0f: A \\rightarrow R$ continuous and <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=K+%5Csubseteq+A&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"K &#92;subseteq A\" class=\"latex\" \/> is compact, then <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f%28k%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f(k)\" class=\"latex\" \/> is compact. We went over a pf of this. Theorem 4.4.2 states that if $latex\u00a0f: K \\rightarrow R$ is continuous on <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=K+%5Csubseteq+R&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"K &#92;subseteq R\" class=\"latex\" \/> compact, then <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\" \/> attains a maximum and minimum on <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=K&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"K\" class=\"latex\" \/>. We then converted this to two equivalent statements, one relating values of <img decoding=\"async\" src=\"https:\/\/s0.wp.com\/latex.php?latex=f%28x%29&#038;bg=ffffff&#038;fg=000&#038;s=0&#038;c=20201002\" alt=\"f(x)\" class=\"latex\" \/> directly and another using supremum and infimum.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>On Thursday 10\/19, we began class with a weekly situation, &#8220;Are we doing mathematics or philosophy?&#8221;. Dr. LeCrone then read a thorough and quite verbose definition of a function from another analysis book. We then switched to the topic of the day: continuity, part of Ch. 4 (Continuity on Compact Sets and Uniform Continuity). We [&hellip;]<\/p>\n","protected":false},"author":3527,"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":[58820,58821],"tags":[],"class_list":["post-1218","post","type-post","status-publish","format-standard","hentry","category-daily-blogs","category-what-happened-today"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7L4E1-jE","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/posts\/1218","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\/3527"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/comments?post=1218"}],"version-history":[{"count":0,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/posts\/1218\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/media?parent=1218"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/categories?post=1218"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.richmond.edu\/math320\/wp-json\/wp\/v2\/tags?post=1218"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}