<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> <meta http-equiv="X-UA-Compatible" content="IE=9"/> <title>Cosine</title> <title>CMSIS-DSP: Cosine</title> <link href="tabs.css" rel="stylesheet" type="text/css"/> <link href="cmsis.css" rel="stylesheet" type="text/css" /> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript" src="dynsections.js"></script> <script type="text/javascript" src="printComponentTabs.js"></script> <link href="navtree.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="resize.js"></script> <script type="text/javascript" src="navtree.js"></script> <script type="text/javascript"> $(document).ready(initResizable); $(window).load(resizeHeight); </script> <link href="search/search.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="search/search.js"></script> <script type="text/javascript"> $(document).ready(function() { searchBox.OnSelectItem(0); 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There are separate functions for Q15, Q31, and floating-point data types. The input to the floating-point version is in radians while the fixed-point Q15 and Q31 have a scaled input with the range [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a value of 2*pi wraps around to 0.</p> <p>The implementation is based on table lookup using 256 values together with linear interpolation. The steps used are:</p> <ol type="1"> <li>Calculation of the nearest integer table index</li> <li>Compute the fractional portion (fract) of the table index.</li> <li>The final result equals <code>(1.0f-fract)*a + fract*b;</code></li> </ol> <p>where </p> <pre> b=Table[index+0]; c=Table[index+1]; </pre> <h2 class="groupheader">Function Documentation</h2> <a class="anchor" id="gace15287f9c64b9b4084d1c797d4c49d8"></a> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> arm_cos_f32 </td> <td>(</td> <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> </td> <td class="paramname"><em>x</em></td><td>)</td> <td></td> </tr> </table> </div><div class="memdoc"> <dl class="params"><dt>Parameters</dt><dd> <table class="params"> <tr><td class="paramdir">[in]</td><td class="paramname">x</td><td>input value in radians. </td></tr> </table> </dd> </dl> <dl class="section return"><dt>Returns</dt><dd>cos(x). </dd></dl> <p>References <a class="el" href="arm__math_8h.html#afcb9147c96853bea484cfc2dde07463d">FAST_MATH_TABLE_SIZE</a>, and <a class="el" href="arm__common__tables_8h.html#a1dec82d596780f1a66ef4f76f137c1d9">sinTable_f32</a>.</p> <p>Referenced by <a class="el" href="arm__sin__cos__example__f32_8c.html#a52d2cba30e6946c95578be946ac12a65">main()</a>.</p> </div> </div> <a class="anchor" id="gadfd60c24def501638c0d5db20f4c869b"></a> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> arm_cos_q15 </td> <td>(</td> <td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> </td> <td class="paramname"><em>x</em></td><td>)</td> <td></td> </tr> </table> </div><div class="memdoc"> <dl class="params"><dt>Parameters</dt><dd> <table class="params"> <tr><td class="paramdir">[in]</td><td class="paramname">x</td><td>Scaled input value in radians. </td></tr> </table> </dd> </dl> <dl class="section return"><dt>Returns</dt><dd>cos(x).</dd></dl> <p>The Q15 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi). </p> <p>References <a class="el" href="arm__math_8h.html#a34716b73c631e65e8dd855e08384ecb2">FAST_MATH_Q15_SHIFT</a>, and <a class="el" href="arm__common__tables_8h.html#a9cbcfe313f61add745ebfeddb4fecd55">sinTable_q15</a>.</p> </div> </div> <a class="anchor" id="gad80f121949ef885a77d83ab36e002567"></a> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> arm_cos_q31 </td> <td>(</td> <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> </td> <td class="paramname"><em>x</em></td><td>)</td> <td></td> </tr> </table> </div><div class="memdoc"> <dl class="params"><dt>Parameters</dt><dd> <table class="params"> <tr><td class="paramdir">[in]</td><td class="paramname">x</td><td>Scaled input value in radians. </td></tr> </table> </dd> </dl> <dl class="section return"><dt>Returns</dt><dd>cos(x).</dd></dl> <p>The Q31 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi). </p> <p>References <a class="el" href="arm__math_8h.html#a4268f77b1811a0c7fc2532a0bf6108b0">FAST_MATH_Q31_SHIFT</a>, and <a class="el" href="arm__common__tables_8h.html#a8bfccee9e1c0042cf4a765f4b19d097d">sinTable_q31</a>.</p> </div> </div> </div><!-- contents --> </div><!-- doc-content --> <!-- start footer part --> <div id="nav-path" class="navpath"><!-- id is needed for treeview function! --> <ul> <li class="footer">Generated on Wed Feb 8 2017 10:20:51 for CMSIS-DSP by ARM Ltd. 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