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  47. <a name="jN"></a>
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  49. <p>
  50. Next: <a href="cbrt.html#cbrt" accesskey="n" rel="next">cbrt</a>, Previous: <a href="atanh.html#atanh" accesskey="p" rel="prev">atanh</a>, Up: <a href="Math.html#Math" accesskey="u" rel="up">Math</a> &nbsp; [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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  53. <a name="jN_002c-jNf_002c-yN_002c-yNf_002d_002d_002dBessel-functions"></a>
  54. <h3 class="section">1.10 <code>jN</code>, <code>jNf</code>, <code>yN</code>, <code>yNf</code>&mdash;Bessel functions</h3>
  55. <a name="index-j0"></a>
  56. <a name="index-j0f"></a>
  57. <a name="index-j1"></a>
  58. <a name="index-j1f"></a>
  59. <a name="index-jn"></a>
  60. <a name="index-jnf"></a>
  61. <a name="index-y0"></a>
  62. <a name="index-y0f"></a>
  63. <a name="index-y1"></a>
  64. <a name="index-y1f"></a>
  65. <a name="index-yn"></a>
  66. <a name="index-ynf"></a>
  67. <p><strong>Synopsis</strong>
  68. </p><div class="example">
  69. <pre class="example">#include &lt;math.h&gt;
  70. double j0(double <var>x</var>);
  71. float j0f(float <var>x</var>);
  72. double j1(double <var>x</var>);
  73. float j1f(float <var>x</var>);
  74. double jn(int <var>n</var>, double <var>x</var>);
  75. float jnf(int <var>n</var>, float <var>x</var>);
  76. double y0(double <var>x</var>);
  77. float y0f(float <var>x</var>);
  78. double y1(double <var>x</var>);
  79. float y1f(float <var>x</var>);
  80. double yn(int <var>n</var>, double <var>x</var>);
  81. float ynf(int <var>n</var>, float <var>x</var>);
  82. </pre></div>
  83. <p><strong>Description</strong><br>
  84. The Bessel functions are a family of functions that solve the
  85. differential equation
  86. </p><div class="smallexample">
  87. <pre class="smallexample"> 2 2 2
  88. x y'' + xy' + (x - p )y = 0
  89. </pre></div>
  90. <p>These functions have many applications in engineering and physics.
  91. </p>
  92. <p><code>jn</code> calculates the Bessel function of the first kind of order
  93. <var>n</var>. <code>j0</code> and <code>j1</code> are special cases for order 0 and order
  94. 1 respectively.
  95. </p>
  96. <p>Similarly, <code>yn</code> calculates the Bessel function of the second kind of
  97. order <var>n</var>, and <code>y0</code> and <code>y1</code> are special cases for order 0 and
  98. 1.
  99. </p>
  100. <p><code>jnf</code>, <code>j0f</code>, <code>j1f</code>, <code>ynf</code>, <code>y0f</code>, and <code>y1f</code> perform the
  101. same calculations, but on <code>float</code> rather than <code>double</code> values.
  102. </p>
  103. <br>
  104. <p><strong>Returns</strong><br>
  105. The value of each Bessel function at <var>x</var> is returned.
  106. </p>
  107. <br>
  108. <p><strong>Portability</strong><br>
  109. None of the Bessel functions are in ANSI C.
  110. </p>
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