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<title>Sinus Cardinal and Hyperbolic Sinus Cardinal Functions Overview</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="math_toolkit.special.sinc.sinc_overview"></a><a class="link" href="sinc_overview.html" title="Sinus Cardinal and Hyperbolic Sinus Cardinal Functions Overview"> Sinus Cardinal
and Hyperbolic Sinus Cardinal Functions Overview</a>
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<p>
The <a href="http://mathworld.wolfram.com/SincFunction.html" target="_top">Sinus Cardinal
family of functions</a> (indexed by the family of indices <code class="literal">a
&gt; 0</code>) is defined by
</p>
<p>
<span class="inlinemediaobject"><img src="../../../../equations/special_functions_blurb20.png"></span>
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<p>
it sees heavy use in signal processing tasks.
</p>
<p>
By analogy, the <a href="http://mathworld.wolfram.com/SinhcFunction.htm" target="_top">Hyperbolic
Sinus Cardinal</a> family of functions (also indexed by the family
of indices <code class="literal">a &gt; 0</code>) is defined by
</p>
<p>
<span class="inlinemediaobject"><img src="../../../../equations/special_functions_blurb22.png"></span>
</p>
<p>
These two families of functions are composed of entire functions.
</p>
<p>
These functions (<a class="link" href="sinc_pi.html" title="sinc_pi">sinc_pi</a>
and <a class="link" href="sinhc_pi.html" title="sinhc_pi">sinhc_pi</a>)
are needed by <a href="http://www.boost.org/libs/math/quaternion/quaternion.html" target="_top">our
implementation</a> of <a href="http://mathworld.wolfram.com/Quaternion.html" target="_top">quaternions</a>
and <a href="http://mathworld.wolfram.com/Octonion.html" target="_top">octonions</a>.
</p>
<div class="blockquote"><blockquote class="blockquote"><p>
<span class="emphasis"><em><span class="bold"><strong>Sinus Cardinal of index pi (purple) and
Hyperbolic Sinus Cardinal of index pi (red) on R</strong></span></em></span>
</p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
<span class="inlinemediaobject"><img src="../../../../graphs/sinc_pi_and_sinhc_pi_on_r.png" alt="sinc_pi_and_sinhc_pi_on_r"></span>
</p></blockquote></div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2006 , 2007, 2008, 2009, 2010 John Maddock, Paul A. Bristow,
Hubert Holin, Xiaogang Zhang, Bruno Lalande, Johan R&#229;de, Gautam Sewani and
Thijs van den Berg<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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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