151 lines
5.6 KiB
HTML
151 lines
5.6 KiB
HTML
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>The GNU Fortran Compiler: ATAN</title>
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Intrinsic-Procedures.html#Intrinsic-Procedures" rel="up" title="Intrinsic Procedures">
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<link href="ATAN2.html#ATAN2" rel="next" title="ATAN2">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="ATAN"></a>
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<div class="header">
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<p>
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Next: <a href="ATAN2.html#ATAN2" accesskey="n" rel="next">ATAN2</a>, Previous: <a href="ASSOCIATED.html#ASSOCIATED" accesskey="p" rel="prev">ASSOCIATED</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="ATAN-_002d_002d_002d-Arctangent-function"></a>
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<h3 class="section">9.21 <code>ATAN</code> — Arctangent function</h3>
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<a name="index-ATAN"></a>
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<a name="index-DATAN"></a>
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<a name="index-trigonometric-function_002c-tangent_002c-inverse"></a>
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<a name="index-tangent_002c-inverse"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p><code>ATAN(X)</code> computes the arctangent of <var>X</var>.
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</p>
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</dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>Fortran 77 and later, for a complex argument and for two arguments
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Fortran 2008 or later
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</p>
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</dd>
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<dt><em>Class</em>:</dt>
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<dd><p>Elemental function
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><table>
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<tr><td width="80%"><code>RESULT = ATAN(X)</code></td></tr>
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<tr><td width="80%"><code>RESULT = ATAN(Y, X)</code></td></tr>
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</table>
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</dd>
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<dt><em>Arguments</em>:</dt>
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<dd><table>
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<tr><td width="15%"><var>X</var></td><td width="70%">The type shall be <code>REAL</code> or <code>COMPLEX</code>;
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if <var>Y</var> is present, <var>X</var> shall be REAL.</td></tr>
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<tr><td width="15%"><var>Y</var> shall be of the same type and kind as <var>X</var>.</td></tr>
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</table>
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</dd>
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<dt><em>Return value</em>:</dt>
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<dd><p>The return value is of the same type and kind as <var>X</var>.
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If <var>Y</var> is present, the result is identical to <code>ATAN2(Y,X)</code>.
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Otherwise, it the arcus tangent of <var>X</var>, where the real part of
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the result is in radians and lies in the range
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<em>-\pi/2 \leq \Re \atan(x) \leq \pi/2</em>.
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</p>
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</dd>
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<dt><em>Example</em>:</dt>
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<dd><div class="smallexample">
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<pre class="smallexample">program test_atan
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real(8) :: x = 2.866_8
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x = atan(x)
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end program test_atan
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</pre></div>
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</dd>
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<dt><em>Specific names</em>:</dt>
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<dd><table>
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<tr><td width="20%">Name</td><td width="20%">Argument</td><td width="20%">Return type</td><td width="25%">Standard</td></tr>
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<tr><td width="20%"><code>ATAN(X)</code></td><td width="20%"><code>REAL(4) X</code></td><td width="20%"><code>REAL(4)</code></td><td width="25%">Fortran 77 and later</td></tr>
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<tr><td width="20%"><code>DATAN(X)</code></td><td width="20%"><code>REAL(8) X</code></td><td width="20%"><code>REAL(8)</code></td><td width="25%">Fortran 77 and later</td></tr>
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</table>
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</dd>
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<dt><em>See also</em>:</dt>
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<dd><p>Inverse function: <a href="TAN.html#TAN">TAN</a>
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</p>
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</dd>
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</dl>
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