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	<id>https://drorbn.net/index.php?action=history&amp;feed=atom&amp;title=0708-1300%2FBarnie_the_polar_bear</id>
	<title>0708-1300/Barnie the polar bear - Revision history</title>
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	<updated>2026-05-05T06:52:16Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
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	<entry>
		<id>https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5916&amp;oldid=prev</id>
		<title>Megan at 16:47, 19 November 2007</title>
		<link rel="alternate" type="text/html" href="https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5916&amp;oldid=prev"/>
		<updated>2007-11-19T16:47:17Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 12:47, 19 November 2007&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 3:&lt;/td&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 3:&lt;/td&gt;
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&lt;tr&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;But, we are going to change a little bit Barnie&#039;s fairy world. We are going to give Barnie two linearly independent vector fields (&amp;lt;math&amp;gt;X&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;Y&amp;lt;/math&amp;gt;) on the earth and Barnie should follow the local flows generated by these vector fields during his journey.&lt;/div&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;But, we are going to change a little bit Barnie&#039;s fairy world. We are going to give Barnie two linearly independent vector fields (&amp;lt;math&amp;gt;X&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;Y&amp;lt;/math&amp;gt;) on the earth and Barnie should follow the local flows generated by these vector fields during his journey.&lt;/div&gt;&lt;/td&gt;
&lt;/tr&gt;
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  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;Pour&lt;/del&gt; Barney! It can happen that at the end of his walk he &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;wont&lt;/del&gt; end at home and he will have to walk a little more to go home. But not too much. In fact, all the ends of his walks form a curve which is almost constant at home!! (&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;its&lt;/del&gt; derivative is zero). The only problem is the second derivative which is twice &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; at home. Even more if &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; is zero then Barnie will be happy again, ending every day at home at the end of his walk.&lt;/div&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;Poor&lt;/ins&gt; Barney! It can happen that at the end of his walk he &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;won&#039;t&lt;/ins&gt; end at home and he will have to walk a little more to go home. But not too much. In fact, all the ends of his walks form a curve which is almost constant at home!! (&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;Its&lt;/ins&gt; derivative is zero). The only problem is the second derivative which is twice &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; at home. Even more if &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; is zero then Barnie will be happy again, ending every day at home at the end of his walk.&lt;/div&gt;&lt;/td&gt;
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  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&#039;&#039;&#039;References&#039;&#039;&#039;&lt;/div&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&#039;&#039;&#039;References&#039;&#039;&#039;&lt;/div&gt;&lt;/td&gt;
&lt;/tr&gt;

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&lt;/table&gt;</summary>
		<author><name>Megan</name></author>
	</entry>
	<entry>
		<id>https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5814&amp;oldid=prev</id>
		<title>Franklin at 13:38, 1 November 2007</title>
		<link rel="alternate" type="text/html" href="https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5814&amp;oldid=prev"/>
		<updated>2007-11-01T13:38:02Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 09:38, 1 November 2007&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 4:&lt;/td&gt;
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  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Pour Barney! It can happen that at the end of his walk he wont end at home and he will have to walk a little more to go home. But not too much. In fact, all the ends of his walks form a curve which is almost constant at home!! (its derivative is zero). The only problem is the second derivative which is twice &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; at home. Even more if &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; is zero then Barnie will be happy again, ending every day at home at the end of his walk.&lt;/div&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Pour Barney! It can happen that at the end of his walk he wont end at home and he will have to walk a little more to go home. But not too much. In fact, all the ends of his walks form a curve which is almost constant at home!! (its derivative is zero). The only problem is the second derivative which is twice &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; at home. Even more if &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; is zero then Barnie will be happy again, ending every day at home at the end of his walk.&lt;/div&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-empty diff-side-deleted&quot;&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-empty diff-side-deleted&quot;&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&#039;&#039;&#039;References&#039;&#039;&#039;&lt;/div&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-empty diff-side-deleted&quot;&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br /&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td colspan=&quot;2&quot; class=&quot;diff-empty diff-side-deleted&quot;&gt;&lt;/td&gt;
  &lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;
  &lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Spivak M. &#039;&#039;A Comprehensive Introduction to Differential Geometry&#039;&#039; Vol 1&lt;/div&gt;&lt;/td&gt;
&lt;/tr&gt;

&lt;!-- diff cache key drordb-drorbn_:diff:wikidiff2:1.12:old-5813:rev-5814:1.13.0 --&gt;
&lt;/table&gt;</summary>
		<author><name>Franklin</name></author>
	</entry>
	<entry>
		<id>https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5813&amp;oldid=prev</id>
		<title>Franklin at 13:36, 1 November 2007</title>
		<link rel="alternate" type="text/html" href="https://drorbn.net/index.php?title=0708-1300/Barnie_the_polar_bear&amp;diff=5813&amp;oldid=prev"/>
		<updated>2007-11-01T13:36:22Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;Barnie is a polar bear. Every morning, Barnie walks to the south x steps then x steps to the east, x to the north and finally x to the west. He do this to keep its shape. He is a little bit lacy and every day he walks for a smaller time, so x is decreasing every time. Of course, every day Barnie ends his trip at home. &lt;br /&gt;
&lt;br /&gt;
But, we are going to change a little bit Barnie&amp;#039;s fairy world. We are going to give Barnie two linearly independent vector fields (&amp;lt;math&amp;gt;X&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;Y&amp;lt;/math&amp;gt;) on the earth and Barnie should follow the local flows generated by these vector fields during his journey.&lt;br /&gt;
&lt;br /&gt;
Pour Barney! It can happen that at the end of his walk he wont end at home and he will have to walk a little more to go home. But not too much. In fact, all the ends of his walks form a curve which is almost constant at home!! (its derivative is zero). The only problem is the second derivative which is twice &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; at home. Even more if &amp;lt;math&amp;gt;[X,Y]&amp;lt;/math&amp;gt; is zero then Barnie will be happy again, ending every day at home at the end of his walk.&lt;/div&gt;</summary>
		<author><name>Franklin</name></author>
	</entry>
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