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<div class="header">
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<a href="#func-members">Functions</a>  </div>
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<div class="title">Cosine</div>  </div>
<div class="ingroups"><a class="el" href="group__group_fast_math.html">Fast Math Functions</a></div></div><!--header-->
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:gace15287f9c64b9b4084d1c797d4c49d8"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__cos.html#gace15287f9c64b9b4084d1c797d4c49d8">arm_cos_f32</a> (<a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> x)</td></tr>
<tr class="memdesc:gace15287f9c64b9b4084d1c797d4c49d8"><td class="mdescLeft">&#160;</td><td class="mdescRight">Fast approximation to the trigonometric cosine function for floating-point data.  <a href="#gace15287f9c64b9b4084d1c797d4c49d8"></a><br/></td></tr>
<tr class="separator:gace15287f9c64b9b4084d1c797d4c49d8"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gadfd60c24def501638c0d5db20f4c869b"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__cos.html#gadfd60c24def501638c0d5db20f4c869b">arm_cos_q15</a> (<a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> x)</td></tr>
<tr class="memdesc:gadfd60c24def501638c0d5db20f4c869b"><td class="mdescLeft">&#160;</td><td class="mdescRight">Fast approximation to the trigonometric cosine function for Q15 data.  <a href="#gadfd60c24def501638c0d5db20f4c869b"></a><br/></td></tr>
<tr class="separator:gadfd60c24def501638c0d5db20f4c869b"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gad80f121949ef885a77d83ab36e002567"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__cos.html#gad80f121949ef885a77d83ab36e002567">arm_cos_q31</a> (<a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> x)</td></tr>
<tr class="memdesc:gad80f121949ef885a77d83ab36e002567"><td class="mdescLeft">&#160;</td><td class="mdescRight">Fast approximation to the trigonometric cosine function for Q31 data.  <a href="#gad80f121949ef885a77d83ab36e002567"></a><br/></td></tr>
<tr class="separator:gad80f121949ef885a77d83ab36e002567"><td class="memSeparator" colspan="2">&#160;</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<p>Computes the trigonometric cosine function using a combination of table lookup and cubic interpolation. 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 cubic interpolation. The steps used are:</p>
<ol type="1">
<li>Calculation of the nearest integer table index</li>
<li>Fetch the four table values a, b, c, and d</li>
<li>Compute the fractional portion (fract) of the table index.</li>
<li>Calculation of wa, wb, wc, wd</li>
<li>The final result equals <code>a*wa + b*wb + c*wc + d*wd</code></li>
</ol>
<p>where </p>
<pre>    
   a=Table[index-1];    
   b=Table[index+0];    
   c=Table[index+1];    
   d=Table[index+2];    
</pre><p> and </p>
<pre>    
   wa=-(1/6)*fract.^3 + (1/2)*fract.^2 - (1/3)*fract;    
   wb=(1/2)*fract.^3 - fract.^2 - (1/2)*fract + 1;    
   wc=-(1/2)*fract.^3+(1/2)*fract.^2+fract;    
   wd=(1/6)*fract.^3 - (1/6)*fract;    
</pre> <h2 class="groupheader">Function Documentation</h2>
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          <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>&#160;</td>
          <td class="paramname"><em>x</em></td><td>)</td>
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<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>
<dl><dt><b>Examples: </b></dt><dd><a class="el" href="arm_sin_cos_example_f32_8c-example.html#a11">arm_sin_cos_example_f32.c</a>.</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_8c.html#a1dec82d596780f1a66ef4f76f137c1d9">sinTable_f32</a>.</p>

<p>Referenced by <a class="el" href="arm__sin__cos__example__f32_8c.html#a52d2cba30e6946c95578be946ac12a65">main()</a>.</p>

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          <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>&#160;</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_8c.html#a9cbcfe313f61add745ebfeddb4fecd55">sinTable_q15</a>.</p>

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          <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>&#160;</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_8c.html#a8bfccee9e1c0042cf4a765f4b19d097d">sinTable_q31</a>.</p>

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