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<title>Overview of the Jacobi Elliptic Functions</title>
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<div class="titlepage"><div><div><h3 class="title">
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<a name="math_toolkit.jacobi.jac_over"></a><a class="link" href="jac_over.html" title="Overview of the Jacobi Elliptic Functions">Overview of the Jacobi
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Elliptic Functions</a>
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</h3></div></div></div>
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<p>
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There are twelve Jacobi Elliptic functions, of which the three copolar functions
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<span class="emphasis"><em>sn</em></span>, <span class="emphasis"><em>cn</em></span> and <span class="emphasis"><em>dn</em></span>
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are the most important as the other nine can be computed from these three
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<a href="#ftn.math_toolkit.jacobi.jac_over.f0" class="footnote" name="math_toolkit.jacobi.jac_over.f0"><sup class="footnote">[2]</sup></a> <a href="#ftn.math_toolkit.jacobi.jac_over.f1" class="footnote" name="math_toolkit.jacobi.jac_over.f1"><sup class="footnote">[3]</sup></a> <a href="#ftn.math_toolkit.jacobi.jac_over.f2" class="footnote" name="math_toolkit.jacobi.jac_over.f2"><sup class="footnote">[4]</sup></a>.
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</p>
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<p>
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These functions each take two arguments: a parameter, and a variable as described
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below.
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</p>
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<p>
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Like all elliptic functions these can be parameterised in a number of ways:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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In terms of a parameter <span class="emphasis"><em>m</em></span>.
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</li>
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<li class="listitem">
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In terms of the elliptic modulus <span class="emphasis"><em>k</em></span> where <span class="emphasis"><em>m
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= k<sup>2</sup></em></span>.
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</li>
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<li class="listitem">
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In terms of the modular angle α, where <span class="emphasis"><em>m = sin<sup>2</sup>  α</em></span>.
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</li>
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</ul></div>
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<p>
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In our implementation, these functions all take the elliptic modulus <span class="emphasis"><em>k</em></span>
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as the parameter.
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</p>
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<p>
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In addition the variable <span class="emphasis"><em>u</em></span> is sometimes expressed as
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an amplitude φ, in our implementation we always use <span class="emphasis"><em>u</em></span>.
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</p>
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<p>
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Finally note that our functions all take the elliptic modulus <span class="emphasis"><em>k</em></span>
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as the <span class="bold"><strong>first</strong></span> argument - this is for alignment
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with the Elliptic Integrals (but is different from other implementations,
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for example Mathworks).
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</p>
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<p>
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A simple example comparing use of <a href="http://www.wolframalpha.com/" target="_top">Wolfram
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Alpha</a> with Boost.Math (including much higher precision using Boost.Multiprecision)
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is <a href="../../../../example/jacobi_zeta_example.cpp" target="_top">jacobi_zeta_example.cpp</a>.
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</p>
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<p>
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There are twelve functions for computing the twelve individual Jacobi elliptic
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functions: <a class="link" href="jacobi_cd.html" title="Jacobi Elliptic Function cd">jacobi_cd</a>,
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<a class="link" href="jacobi_cn.html" title="Jacobi Elliptic Function cn">jacobi_cn</a>, <a class="link" href="jacobi_cs.html" title="Jacobi Elliptic Function cs">jacobi_cs</a>,
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<a class="link" href="jacobi_dc.html" title="Jacobi Elliptic Function dc">jacobi_dc</a>, <a class="link" href="jacobi_dn.html" title="Jacobi Elliptic Function dn">jacobi_dn</a>,
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<a class="link" href="jacobi_ds.html" title="Jacobi Elliptic Function ds">jacobi_ds</a>, <a class="link" href="jacobi_nc.html" title="Jacobi Elliptic Function nc">jacobi_nc</a>,
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<a class="link" href="jacobi_nd.html" title="Jacobi Elliptic Function nd">jacobi_nd</a>, <a class="link" href="jacobi_ns.html" title="Jacobi Elliptic Function ns">jacobi_ns</a>,
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<a class="link" href="jacobi_sc.html" title="Jacobi Elliptic Function sc">jacobi_sc</a>, <a class="link" href="jacobi_sd.html" title="Jacobi Elliptic Function sd">jacobi_sd</a>
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and <a class="link" href="jacobi_sn.html" title="Jacobi Elliptic Function sn">jacobi_sn</a>.
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</p>
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<p>
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They are all called as for example:
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</p>
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<pre class="programlisting"><span class="identifier">jacobi_cs</span><span class="special">(</span><span class="identifier">k</span><span class="special">,</span> <span class="identifier">u</span><span class="special">);</span>
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</pre>
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<p>
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Note however that these individual functions are all really thin wrappers
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around the function <a class="link" href="jacobi_elliptic.html" title="Jacobi Elliptic SN, CN and DN">jacobi_elliptic</a>
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which calculates the three copolar functions <span class="emphasis"><em>sn</em></span>, <span class="emphasis"><em>cn</em></span>
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and <span class="emphasis"><em>dn</em></span> in a single function call.
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</p>
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<div class="tip"><table border="0" summary="Tip">
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<tr>
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td>
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<th align="left">Tip</th>
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</tr>
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<tr><td align="left" valign="top"><p>
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If you need more than one of these functions for a given set of arguments,
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it's most efficient to use <a class="link" href="jacobi_elliptic.html" title="Jacobi Elliptic SN, CN and DN">jacobi_elliptic</a>.
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</p></td></tr>
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</table></div>
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<div class="footnotes">
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<br><hr style="width:100; text-align:left;margin-left: 0">
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<div id="ftn.math_toolkit.jacobi.jac_over.f0" class="footnote"><p><a href="#math_toolkit.jacobi.jac_over.f0" class="para"><sup class="para">[2] </sup></a>
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<a href="http://en.wikipedia.org/wiki/Jacobi_elliptic_functions" target="_top">Wikipedia:
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Jacobi elliptic functions</a>
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</p></div>
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<div id="ftn.math_toolkit.jacobi.jac_over.f1" class="footnote"><p><a href="#math_toolkit.jacobi.jac_over.f1" class="para"><sup class="para">[3] </sup></a>
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<a href="http://mathworld.wolfram.com/JacobiEllipticFunctions.html" target="_top">Weisstein,
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Eric W. "Jacobi Elliptic Functions." From MathWorld - A Wolfram
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Web Resource.</a>
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</p></div>
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<div id="ftn.math_toolkit.jacobi.jac_over.f2" class="footnote"><p><a href="#math_toolkit.jacobi.jac_over.f2" class="para"><sup class="para">[4] </sup></a>
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<a href="http://dlmf.nist.gov/22" target="_top">Digital Library of Mathematical Functions:
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Jacobian Elliptic Functions, Reinhardt, W. P., Walker, O. L.</a>
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</p></div>
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</div>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2006-2019 Nikhar
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Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos,
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Hubert Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Matthew Pulver, Johan
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Råde, Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg,
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Daryle Walker and Xiaogang Zhang<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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</p>
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