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<a name="Trigonometric"></a>
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<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
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</tr></table>
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<h1 class="chapter"> 15. Trigonometric </h1>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top"><a href="#SEC52">15.1 Introduction to Trigonometric</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">  
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</td></tr>
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<tr><td align="left" valign="top"><a href="#SEC53">15.2 Definitions for Trigonometric</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">  
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</td></tr>
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</table>
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<hr size="6">
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<a name="Introduction-to-Trigonometric"></a>
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<a name="SEC52"></a>
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<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
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</tr></table>
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<h2 class="section"> 15.1 Introduction to Trigonometric </h2>
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<p>Maxima has many trigonometric functions defined.  Not all trigonometric
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identities are programmed, but it is possible for the user to add many
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of them using the pattern matching capabilities of the system.  The
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trigonometric functions defined in Maxima are: <code>acos</code>,
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<code>acosh</code>, <code>acot</code>, <code>acoth</code>, <code>acsc</code>,
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<code>acsch</code>, <code>asec</code>, <code>asech</code>, <code>asin</code>, 
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<code>asinh</code>, <code>atan</code>, <code>atanh</code>, <code>cos</code>, 
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<code>cosh</code>, <code>cot</code>, <code>coth</code>, <code>csc</code>, <code>csch</code>, 
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<code>sec</code>, <code>sech</code>, <code>sin</code>, <code>sinh</code>, <code>tan</code>, 
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and <code>tanh</code>.  There are a number of commands especially for 
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handling trigonometric functions, see <code>trigexpand</code>,
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<code>trigreduce</code>, and the switch <code>trigsign</code>.  Two share 
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packages extend the simplification rules built into Maxima, 
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<code>ntrig</code> and <code>atrig1</code>.  Do <code>describe(<var>command</var>)</code>
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for details.
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</p>
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<hr size="6">
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<a name="Definitions-for-Trigonometric"></a>
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<a name="SEC53"></a>
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<table cellpadding="1" cellspacing="1" border="0">
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<tr><td valign="middle" align="left">[<a href="#SEC52" title="Previous section in reading order"> &lt; </a>]</td>
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<td valign="middle" align="left">[<a href="maxima_16.html#SEC54" title="Next section in reading order"> &gt; </a>]</td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left">[<a href="#SEC51" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC51" title="Up section"> Up </a>]</td>
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<td valign="middle" align="left">[<a href="maxima_16.html#SEC54" title="Next chapter"> &gt;&gt; </a>]</td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_72.html#SEC264" title="Index">Index</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
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</tr></table>
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<h2 class="section"> 15.2 Definitions for Trigonometric </h2>
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<dl>
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<dt><u>Function:</u> <b>acos</b><i> (<var>x</var>)</i>
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<a name="IDX475"></a>
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</dt>
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<dd><p> - Arc Cosine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>acosh</b><i> (<var>x</var>)</i>
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<a name="IDX476"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Cosine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>acot</b><i> (<var>x</var>)</i>
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<a name="IDX477"></a>
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</dt>
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<dd><p> - Arc Cotangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>acoth</b><i> (<var>x</var>)</i>
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<a name="IDX478"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Cotangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>acsc</b><i> (<var>x</var>)</i>
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<a name="IDX479"></a>
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</dt>
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<dd><p> - Arc Cosecant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>acsch</b><i> (<var>x</var>)</i>
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<a name="IDX480"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Cosecant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>asec</b><i> (<var>x</var>)</i>
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<a name="IDX481"></a>
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</dt>
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<dd><p> - Arc Secant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>asech</b><i> (<var>x</var>)</i>
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<a name="IDX482"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Secant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>asin</b><i> (<var>x</var>)</i>
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<a name="IDX483"></a>
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</dt>
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<dd><p> - Arc Sine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>asinh</b><i> (<var>x</var>)</i>
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<a name="IDX484"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Sine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>atan</b><i> (<var>x</var>)</i>
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<a name="IDX485"></a>
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</dt>
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<dd><p> - Arc Tangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>atan2</b><i> (<var>y</var>, <var>x</var>)</i>
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<a name="IDX486"></a>
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</dt>
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<dd><p>- yields the value of <code>atan(<var>y</var>/<var>x</var>)</code> in the interval <code>-%pi</code> to
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<code>%pi</code>.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>atanh</b><i> (<var>x</var>)</i>
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<a name="IDX487"></a>
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</dt>
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<dd><p> - Hyperbolic Arc Tangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Package:</u> <b>atrig1</b>
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<a name="IDX488"></a>
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</dt>
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<dd><p>The <code>atrig1</code> package contains several additional simplification rules 
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for inverse trigonometric functions.  Together with rules
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already known to Maxima, the following angles are fully implemented:
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<code>0</code>, <code>%pi/6</code>, <code>%pi/4</code>, <code>%pi/3</code>, and <code>%pi/2</code>.  
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Corresponding angles in the other three quadrants are also available.  
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Do <code>load(atrig1);</code> to use them.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>cos</b><i> (<var>x</var>)</i>
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<a name="IDX489"></a>
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</dt>
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<dd><p> - Cosine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>cosh</b><i> (<var>x</var>)</i>
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<a name="IDX490"></a>
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</dt>
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<dd><p> - Hyperbolic Cosine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>cot</b><i> (<var>x</var>)</i>
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<a name="IDX491"></a>
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</dt>
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<dd><p> - Cotangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>coth</b><i> (<var>x</var>)</i>
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<a name="IDX492"></a>
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</dt>
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<dd><p> - Hyperbolic Cotangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>csc</b><i> (<var>x</var>)</i>
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<a name="IDX493"></a>
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</dt>
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<dd><p> - Cosecant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>csch</b><i> (<var>x</var>)</i>
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<a name="IDX494"></a>
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</dt>
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<dd><p> - Hyperbolic Cosecant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Option variable:</u> <b>halfangles</b>
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<a name="IDX495"></a>
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</dt>
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<dd><p>Default value: <code>false</code>
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</p>
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<p>When <code>halfangles</code> is <code>true</code>,
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half-angles are simplified away.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Package:</u> <b>ntrig</b>
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<a name="IDX496"></a>
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</dt>
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<dd><p>The <code>ntrig</code> package contains a set of simplification rules that are
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used to simplify trigonometric function whose arguments are of the form
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<code><var>f</var>(<var>n</var> %pi/10)</code> where <var>f</var> is any of the functions 
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<code>sin</code>, <code>cos</code>, <code>tan</code>, <code>csc</code>, <code>sec</code> and <code>cot</code>.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>sec</b><i> (<var>x</var>)</i>
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<a name="IDX497"></a>
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</dt>
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<dd><p> - Secant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>sech</b><i> (<var>x</var>)</i>
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<a name="IDX498"></a>
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</dt>
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<dd><p> - Hyperbolic Secant.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>sin</b><i> (<var>x</var>)</i>
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<a name="IDX499"></a>
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</dt>
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<dd><p> - Sine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>sinh</b><i> (<var>x</var>)</i>
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<a name="IDX500"></a>
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</dt>
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<dd><p> - Hyperbolic Sine.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>tan</b><i> (<var>x</var>)</i>
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<a name="IDX501"></a>
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</dt>
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<dd><p> - Tangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>tanh</b><i> (<var>x</var>)</i>
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<a name="IDX502"></a>
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</dt>
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<dd><p> - Hyperbolic Tangent.
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</p>
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</dd></dl>
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<dl>
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<dt><u>Function:</u> <b>trigexpand</b><i> (<var>expr</var>)</i>
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<a name="IDX503"></a>
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</dt>
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<dd><p>Expands trigonometric and hyperbolic functions of
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sums of angles and of multiple angles occurring in <var>expr</var>.  For best
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results, <var>expr</var> should be expanded.  To enhance user control of
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simplification, this function expands only one level at a time,
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expanding sums of angles or multiple angles.  To obtain full expansion
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into sines and cosines immediately, set the switch <code>trigexpand: true</code>.
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</p>
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<p><code>trigexpand</code> is governed by the following global flags:
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</p>
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<dl compact="compact">
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<dt> <code>trigexpand</code></dt>
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<dd><p>If <code>true</code> causes expansion of all
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expressions containing sin's and cos's occurring subsequently.
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</p></dd>
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<dt> <code>halfangles</code></dt>
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<dd><p>If <code>true</code> causes half-angles to be simplified
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away.
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</p></dd>
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<dt> <code>trigexpandplus</code></dt>
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<dd><p>Controls the &quot;sum&quot; rule for <code>trigexpand</code>,
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expansion of sums (e.g. <code>sin(x + y)</code>) will take place only if
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<code>trigexpandplus</code> is <code>true</code>.
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</p></dd>
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<dt> <code>trigexpandtimes</code></dt>
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<dd><p>Controls the &quot;product&quot; rule for <code>trigexpand</code>,
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expansion of products (e.g. <code>sin(2 x)</code>) will take place only if
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<code>trigexpandtimes</code> is <code>true</code>.
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</p></dd>
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</dl>
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<p>Examples:
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</p>
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<table><tr><td>&nbsp;</td><td><pre class="example">(%i1) x+sin(3*x)/sin(x),trigexpand=true,expand;
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                         2           2
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(%o1)               - sin (x) + 3 cos (x) + x
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(%i2) trigexpand(sin(10*x+y));
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(%o2)          cos(10 x) sin(y) + sin(10 x) cos(y)
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</pre></td></tr></table>
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</dd></dl>
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<dl>
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<dt><u>Option variable:</u> <b>trigexpandplus</b>
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<a name="IDX504"></a>
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</dt>
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<dd><p>Default value: <code>true</code>
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</p>
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<p><code>trigexpandplus</code> controls the &quot;sum&quot; rule for
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<code>trigexpand</code>.  Thus, when the <code>trigexpand</code> command is used or the
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<code>trigexpand</code> switch set to <code>true</code>, expansion of sums 
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(e.g. <code>sin(x+y))</code> will take place only if <code>trigexpandplus</code> is 
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<code>true</code>.
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</p>
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</dd></dl>
511
512
<dl>
513
<dt><u>Option variable:</u> <b>trigexpandtimes</b>
514
<a name="IDX505"></a>
515
</dt>
516
<dd><p>Default value: <code>true</code>
517
</p>
518
<p><code>trigexpandtimes</code> controls the &quot;product&quot; rule for
519
<code>trigexpand</code>.  Thus, when the <code>trigexpand</code> command is used or the
520
<code>trigexpand</code> switch set to <code>true</code>, expansion of products (e.g. <code>sin(2*x)</code>)
521
will take place only if <code>trigexpandtimes</code> is <code>true</code>.
522
</p>
523
</dd></dl>
524
525
<dl>
526
<dt><u>Option variable:</u> <b>triginverses</b>
527
<a name="IDX506"></a>
528
</dt>
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<dd><p>Default value: <code>all</code>
530
</p>
531
<p><code>triginverses</code> controls the simplification of the
532
composition of trigonometric and hyperbolic functions with their inverse
533
functions.
534
</p>
535
<p>If <code>all</code>, both e.g. <code>atan(tan(<var>x</var>))</code> 
536
and <code>tan(atan(<var>x</var>))</code> simplify to <var>x</var>.  
537
</p>
538
<p>If <code>true</code>, the <code><var>arcfun</var>(<var>fun</var>(<var>x</var>))</code> 
539
simplification is turned off.
540
</p>
541
<p>If <code>false</code>, both the 
542
<code><var>arcfun</var>(<var>fun</var>(<var>x</var>))</code> and 
543
<code><var>fun</var>(<var>arcfun</var>(<var>x</var>))</code>
544
simplifications are turned off.
545
</p>
546
</dd></dl>
547
548
<dl>
549
<dt><u>Function:</u> <b>trigreduce</b><i> (<var>expr</var>, <var>x</var>)</i>
550
<a name="IDX507"></a>
551
</dt>
552
<dt><u>Function:</u> <b>trigreduce</b><i> (<var>expr</var>)</i>
553
<a name="IDX508"></a>
554
</dt>
555
<dd><p>Combines products and powers of trigonometric
556
and hyperbolic sin's and cos's of <var>x</var> into those of multiples of <var>x</var>.
557
It also tries to eliminate these functions when they occur in
558
denominators.  If <var>x</var> is omitted then all variables in <var>expr</var> are used.
559
</p>
560
<p>See also <code>poissimp</code>.
561
</p>
562
<table><tr><td>&nbsp;</td><td><pre class="example">(%i1) trigreduce(-sin(x)^2+3*cos(x)^2+x);
563
               cos(2 x)      cos(2 x)   1        1
564
(%o1)          -------- + 3 (-------- + -) + x - -
565
                  2             2       2        2
566
567
</pre></td></tr></table>
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<p>The trigonometric simplification routines will use declared
569
information in some simple cases.  Declarations about variables are
570
used as follows, e.g.
571
</p>
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<table><tr><td>&nbsp;</td><td><pre class="example">(%i1) declare(j, integer, e, even, o, odd)$
573
(%i2) sin(x + (e + 1/2)*%pi);
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(%o2)                        cos(x)
575
(%i3) sin(x + (o + 1/2)*%pi);
576
(%o3)                       - cos(x)
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</pre></td></tr></table>
579
</dd></dl>
580
581
<dl>
582
<dt><u>Option variable:</u> <b>trigsign</b>
583
<a name="IDX509"></a>
584
</dt>
585
<dd><p>Default value: <code>true</code>
586
</p>
587
<p>When <code>trigsign</code> is <code>true</code>, it permits simplification of negative
588
arguments to trigonometric functions. E.g., <code>sin(-x)</code> will become
589
<code>-sin(x)</code> only if <code>trigsign</code> is <code>true</code>.
590
</p>
591
</dd></dl>
592
593
<dl>
594
<dt><u>Function:</u> <b>trigsimp</b><i> (<var>expr</var>)</i>
595
<a name="IDX510"></a>
596
</dt>
597
<dd><p>Employs the identities <em>sin(x)^2 + cos(x)^2 = 1</em> and
598
<em>cosh(x)^2 - sinh(x)^2 = 1</em> to simplify expressions containing <code>tan</code>, <code>sec</code>,
599
etc., to <code>sin</code>, <code>cos</code>, <code>sinh</code>, <code>cosh</code>.
600
</p>
601
<p><code>trigreduce</code>, <code>ratsimp</code>, and <code>radcan</code> may be
602
able to further simplify the result.
603
</p>
604
<p><code>demo (&quot;trgsmp.dem&quot;)</code> displays some examples of <code>trigsimp</code>.
605
</p>
606
</dd></dl>
607
608
<dl>
609
<dt><u>Function:</u> <b>trigrat</b><i> (<var>expr</var>)</i>
610
<a name="IDX511"></a>
611
</dt>
612
<dd><p>Gives a canonical simplifyed quasilinear form of a
613
trigonometrical expression; <var>expr</var> is a rational fraction of several <code>sin</code>,
614
<code>cos</code> or <code>tan</code>, the arguments of them are linear forms in some variables (or
615
kernels) and <code>%pi/<var>n</var></code> (<var>n</var> integer) with integer coefficients. The result is a
616
simplified fraction with numerator and denominator linear in <code>sin</code> and <code>cos</code>.
617
Thus <code>trigrat</code> linearize always when it is possible.
618
</p>
619
<table><tr><td>&nbsp;</td><td><pre class="example">(%i1) trigrat(sin(3*a)/sin(a+%pi/3));
620
(%o1)            sqrt(3) sin(2 a) + cos(2 a) - 1
621
622
</pre></td></tr></table>
623
<p>The following example is taken from
624
Davenport, Siret, and Tournier, <i>Calcul Formel</i>, Masson (or in English,
625
Addison-Wesley), section 1.5.5, Morley theorem.
626
</p>
627
<table><tr><td>&nbsp;</td><td><pre class="example">(%i1) c: %pi/3 - a - b;
628
                                    %pi
629
(%o1)                     - b - a + ---
630
                                     3
631
(%i2) bc: sin(a)*sin(3*c)/sin(a+b);
632
                      sin(a) sin(3 b + 3 a)
633
(%o2)                 ---------------------
634
                           sin(b + a)
635
(%i3) ba: bc, c=a, a=c$
636
(%i4) ac2: ba^2 + bc^2 - 2*bc*ba*cos(b);
637
         2       2
638
      sin (a) sin (3 b + 3 a)
639
(%o4) -----------------------
640
               2
641
            sin (b + a)
642
643
                                        %pi
644
   2 sin(a) sin(3 a) cos(b) sin(b + a - ---) sin(3 b + 3 a)
645
                                         3
646
 - --------------------------------------------------------
647
                           %pi
648
                   sin(a - ---) sin(b + a)
649
                            3
650
651
      2         2         %pi
652
   sin (3 a) sin (b + a - ---)
653
                           3
654
 + ---------------------------
655
             2     %pi
656
          sin (a - ---)
657
                    3
658
(%i5) trigrat (ac2);
659
(%o5) - (sqrt(3) sin(4 b + 4 a) - cos(4 b + 4 a)
660
661
 - 2 sqrt(3) sin(4 b + 2 a) + 2 cos(4 b + 2 a)
662
663
 - 2 sqrt(3) sin(2 b + 4 a) + 2 cos(2 b + 4 a)
664
665
 + 4 sqrt(3) sin(2 b + 2 a) - 8 cos(2 b + 2 a) - 4 cos(2 b - 2 a)
666
667
 + sqrt(3) sin(4 b) - cos(4 b) - 2 sqrt(3) sin(2 b) + 10 cos(2 b)
668
669
 + sqrt(3) sin(4 a) - cos(4 a) - 2 sqrt(3) sin(2 a) + 10 cos(2 a)
670
671
 - 9)/4
672
673
</pre></td></tr></table>
674
</dd></dl>
675
676
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<hr size="6">
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<table cellpadding="1" cellspacing="1" border="0">
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<tr><td valign="middle" align="left">[<a href="#SEC51" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left"> &nbsp; </td>
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<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_72.html#SEC264" title="Index">Index</a>]</td>
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<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
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</tr></table>
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<p>
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