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+<page xmlns="http://projectmallard.org/1.0/"
+      type="guide"
+      id="variable">
+
+    <info>
+        <link type="guide" xref="index#equation"/>
+    </info>
+
+	<title>Variables</title>
+    
+    <p>
+    To assign a value to a variable use the = symbol or choose the variable to assign to with the <gui>→R</gui> button in <link xref="mouse">advanced mode</link>.
+    A variable name must only contain upper or lower characters.
+    </p>
+    <example>
+    <p>
+    x=5
+    </p>
+    <p>
+    value=82
+    </p>
+    </example>
+    <p>
+    Variables can be used in any equation and are substituted for their assigned value.
+    Variables can be inserted using the <gui>←R</gui> button.
+    </p>
+    <example>
+    <p>
+    6x+3
+    </p>
+    <p>
+    xy−3x+7y−21
+    </p>
+    </example>
+    <p>
+    The following variables are always defined.
+    </p>
+    <table>
+    <tr>
+    <td><p>ans</p></td>
+    <td><p>Result of previous calculation</p></td>
+    </tr>
+    <tr>
+    <td><p>e</p></td>
+    <td><p><link xref="logarithm">Euler's Number</link></p></td>
+    </tr>
+    <tr>
+    <td><p>π</p></td>
+    <td><p><link xref="trigonometry">Pi</link></p></td>
+    </tr>
+    <tr>
+    <td><p>rand</p></td>
+    <td><p>Random value in the range [0,1] (changes on each read)</p></td>
+    </tr>
+    </table>
+</page>