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	<id>https://companal.subwiki.org/w/index.php?action=history&amp;feed=atom&amp;title=Cauchy-Riemann_differential_equations</id>
	<title>Cauchy-Riemann differential equations - Revision history</title>
	<link rel="self" type="application/atom+xml" href="https://companal.subwiki.org/w/index.php?action=history&amp;feed=atom&amp;title=Cauchy-Riemann_differential_equations"/>
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	<updated>2026-05-21T07:44:20Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
	<generator>MediaWiki 1.41.2</generator>
	<entry>
		<id>https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=38&amp;oldid=prev</id>
		<title>Vipul: 3 revisions</title>
		<link rel="alternate" type="text/html" href="https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=38&amp;oldid=prev"/>
		<updated>2008-05-18T19:10:12Z</updated>

		<summary type="html">&lt;p&gt;3 revisions&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;1&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;1&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 19:10, 18 May 2008&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-notice&quot; lang=&quot;en&quot;&gt;&lt;div class=&quot;mw-diff-empty&quot;&gt;(No difference)&lt;/div&gt;
&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;</summary>
		<author><name>Vipul</name></author>
	</entry>
	<entry>
		<id>https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=37&amp;oldid=prev</id>
		<title>Vipul at 00:49, 18 April 2008</title>
		<link rel="alternate" type="text/html" href="https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=37&amp;oldid=prev"/>
		<updated>2008-04-18T00:49:17Z</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;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&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 00:49, 18 April 2008&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l13&quot;&gt;Line 13:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 13:&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;{{quotation|&amp;lt;math&amp;gt;u_x = v_y, \qquad u_y = -v_x&amp;lt;/math&amp;gt;}}&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;{{quotation|&amp;lt;math&amp;gt;u_x = v_y, \qquad u_y = -v_x&amp;lt;/math&amp;gt;}}&lt;/div&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;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;Note that if we are given that &amp;lt;math&amp;gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;u&lt;/del&gt;&amp;lt;/math&amp;gt; &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;and &lt;/del&gt;&amp;lt;math&amp;gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;v&lt;/del&gt;&amp;lt;/math&amp;gt; &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;are both continuously differentiable &lt;/del&gt;in the real sense, then satisfying the Cauchy-Riemann differential equations at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt; is equivalent to being complex-differentiable at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt;.&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;We can talk of a [[function satisfying Cauchy-Riemann differential equations at a point]].&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;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;Note that if we are given that &amp;lt;math&amp;gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;f&lt;/ins&gt;&amp;lt;/math&amp;gt; &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;is differentiable at &lt;/ins&gt;&amp;lt;math&amp;gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;z_0&lt;/ins&gt;&amp;lt;/math&amp;gt; in the real sense, then satisfying the Cauchy-Riemann differential equations at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt; is equivalent to being complex-differentiable at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt;. &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;{proofat|[[Real-differentiable and Cauchy-Riemann equals complex-differentiable]]}}&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vipul</name></author>
	</entry>
	<entry>
		<id>https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=36&amp;oldid=prev</id>
		<title>Vipul: /* Definition */</title>
		<link rel="alternate" type="text/html" href="https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=36&amp;oldid=prev"/>
		<updated>2008-04-13T21:16:05Z</updated>

		<summary type="html">&lt;p&gt;&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Definition&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&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 21:16, 13 April 2008&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l7&quot;&gt;Line 7:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 7:&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;We say that &amp;lt;math&amp;gt;f&amp;lt;/math&amp;gt; satisfies the &amp;#039;&amp;#039;&amp;#039;Cauchy-Riemann differential equations&amp;#039;&amp;#039;&amp;#039; at a point &amp;lt;math&amp;gt;z_0 \in U&amp;lt;/math&amp;gt; if the partial derivatives of the &amp;lt;math&amp;gt;u,v&amp;lt;/math&amp;gt; in both the &amp;lt;math&amp;gt;x&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;y&amp;lt;/math&amp;gt; directions exist, and satisfy the following conditions:&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;We say that &amp;lt;math&amp;gt;f&amp;lt;/math&amp;gt; satisfies the &amp;#039;&amp;#039;&amp;#039;Cauchy-Riemann differential equations&amp;#039;&amp;#039;&amp;#039; at a point &amp;lt;math&amp;gt;z_0 \in U&amp;lt;/math&amp;gt; if the partial derivatives of the &amp;lt;math&amp;gt;u,v&amp;lt;/math&amp;gt; in both the &amp;lt;math&amp;gt;x&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;y&amp;lt;/math&amp;gt; directions exist, and satisfy the following conditions:&lt;/div&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;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;&amp;lt;math&amp;gt;\frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \frac{\partial u}{\partial y} = - \frac{\partial v}{\partial x}&amp;lt;/math&amp;gt;&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;{{quotation|&lt;/ins&gt;&amp;lt;math&amp;gt;\frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \frac{\partial u}{\partial y} = - \frac{\partial v}{\partial x}&amp;lt;/math&amp;gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;}}&lt;/ins&gt;&lt;/div&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;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;Using the subscript notation for partial derivatives, we can write this more compactly as:&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;Using the subscript notation for partial derivatives, we can write this more compactly as:&lt;/div&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;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;&amp;lt;math&amp;gt;u_x = v_y, u_y = -v_x&amp;lt;/math&amp;gt;&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;{{quotation|&lt;/ins&gt;&amp;lt;math&amp;gt;u_x = v_y, &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;\qquad &lt;/ins&gt;u_y = -v_x&amp;lt;/math&amp;gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;}}&lt;/ins&gt;&lt;/div&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;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;Note that if we are given that &amp;lt;math&amp;gt;u&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;v&amp;lt;/math&amp;gt; are both continuously differentiable in the real sense, then satisfying the Cauchy-Riemann differential equations at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt; is equivalent to being complex-differentiable at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt;.&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;Note that if we are given that &amp;lt;math&amp;gt;u&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;v&amp;lt;/math&amp;gt; are both continuously differentiable in the real sense, then satisfying the Cauchy-Riemann differential equations at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt; is equivalent to being complex-differentiable at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt;.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vipul</name></author>
	</entry>
	<entry>
		<id>https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=35&amp;oldid=prev</id>
		<title>Vipul: New page: ==Definition==  Suppose &lt;math&gt;U&lt;/math&gt; is an open subset of &lt;math&gt;\mathbb{C}&lt;/math&gt; and &lt;math&gt;f:U \to \mathbb{C}&lt;/math&gt; is a function. Write &lt;math&gt;f&lt;/math&gt; in terms of its real and imagina...</title>
		<link rel="alternate" type="text/html" href="https://companal.subwiki.org/w/index.php?title=Cauchy-Riemann_differential_equations&amp;diff=35&amp;oldid=prev"/>
		<updated>2008-04-13T21:05:40Z</updated>

		<summary type="html">&lt;p&gt;New page: ==Definition==  Suppose &amp;lt;math&amp;gt;U&amp;lt;/math&amp;gt; is an open subset of &amp;lt;math&amp;gt;\mathbb{C}&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;f:U \to \mathbb{C}&amp;lt;/math&amp;gt; is a function. Write &amp;lt;math&amp;gt;f&amp;lt;/math&amp;gt; in terms of its real and imagina...&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;==Definition==&lt;br /&gt;
&lt;br /&gt;
Suppose &amp;lt;math&amp;gt;U&amp;lt;/math&amp;gt; is an open subset of &amp;lt;math&amp;gt;\mathbb{C}&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;f:U \to \mathbb{C}&amp;lt;/math&amp;gt; is a function. Write &amp;lt;math&amp;gt;f&amp;lt;/math&amp;gt; in terms of its real and imaginary parts as follows:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;math&amp;gt;f(z) := u(z) + iv(z)&amp;lt;/math&amp;gt;&lt;br /&gt;
&lt;br /&gt;
We say that &amp;lt;math&amp;gt;f&amp;lt;/math&amp;gt; satisfies the &amp;#039;&amp;#039;&amp;#039;Cauchy-Riemann differential equations&amp;#039;&amp;#039;&amp;#039; at a point &amp;lt;math&amp;gt;z_0 \in U&amp;lt;/math&amp;gt; if the partial derivatives of the &amp;lt;math&amp;gt;u,v&amp;lt;/math&amp;gt; in both the &amp;lt;math&amp;gt;x&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;y&amp;lt;/math&amp;gt; directions exist, and satisfy the following conditions:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;math&amp;gt;\frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \frac{\partial u}{\partial y} = - \frac{\partial v}{\partial x}&amp;lt;/math&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Using the subscript notation for partial derivatives, we can write this more compactly as:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;math&amp;gt;u_x = v_y, u_y = -v_x&amp;lt;/math&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Note that if we are given that &amp;lt;math&amp;gt;u&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;v&amp;lt;/math&amp;gt; are both continuously differentiable in the real sense, then satisfying the Cauchy-Riemann differential equations at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt; is equivalent to being complex-differentiable at &amp;lt;math&amp;gt;z_0&amp;lt;/math&amp;gt;.&lt;/div&gt;</summary>
		<author><name>Vipul</name></author>
	</entry>
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