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+<page xmlns="http://projectmallard.org/1.0/"
+      type="guide"
+      id="trigonometry">
+
+    <info>
+        <link type="guide" xref="index#equation"/>
+    </info>
+
+	<title>Trigonometry</title>
+    
+    <p>
+    Trigonometry can be performed using the sin, cos, and tan <link xref="function">function</link>.
+    </p>
+    <example>
+    <p>
+    sin 45
+    </p>
+    </example>
+    <p>
+    The angle units used can be changed from the <guiseq><gui>Calculator</gui><gui>Preferences</gui></guiseq> menu.
+    Trigonometry buttons are visible when in <link xref="mouse">scientific mode</link>.
+    </p>
+    <p>
+    Hyperbolic functions are available by adding "h" to the end of a function.
+    </p>
+    <example>
+    <p>
+    sinh 0.34
+    </p>
+    </example>
+    <p>
+    Inverse functions are entered either using the inverse symbol ⁻¹ (<keyseq><key>Ctrl</key><key>I</key></keyseq>) or the "a" form of the function.
+    The following two equations are equivalent.
+    </p>
+    <example>
+    <p>
+    sin⁻¹ 0.5
+    </p>
+    <p>
+    asin 0.5 
+    </p>
+    </example>   
+    <p>
+    To enter <link xref="variable">π</link> with the keyboard use <keyseq><key>Ctrl</key><key>P</key></keyseq>.
+    </p>
+</page>