240 lines
12 KiB
HTML
240 lines
12 KiB
HTML
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<title>tanh, tanhf, tanhl</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_numeric_math_tanh skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading">tanh, tanhf, tanhl</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-numeric.html">numeric</a>‎ | <a href="c-numeric-math.html">math</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<td>
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<div>定义于头文件 <code><math.h></code></div>
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</td>
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<td></td>
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<td></td>
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<div><span class="mw-geshi c source-c"><span class="kw4">float</span> tanhf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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<div><span class="mw-geshi c source-c"><span class="kw4">double</span> tanh<span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">double</span> tanhl<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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<td>
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<div>定义于头文件 <code><tgmath.h></code></div>
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</td>
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<td></td>
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<td></td>
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<div><span class="mw-geshi c source-c"><span class="co2">#define tanh( arg )</span></span></div>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tbody>
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<div class="t-li1"><span class="t-li">1-3)</span> 计算 <code>arg</code> 的双曲正切。</div>
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<div class="t-li1"><span class="t-li">4)</span> 泛型宏：若参数拥有 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">double</span></span></span> 类型，则调用 <code>tanhl</code> 。否则，若参数拥有整数类型或 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">double</span></span></span> 类型，则调用 <code>tanh</code> 。否则调用 <code>tanhf</code> 若参数为复数，则宏调用对应的复数函数（ <span class="t-c"><span class="mw-geshi c source-c"><a href="c-numeric-complex-ctanh.html"><span class="kw814">ctanhf</span></a></span></span> 、 <span class="t-c"><span class="mw-geshi c source-c"><a href="c-numeric-complex-ctanh.html"><span class="kw813">ctanh</span></a></span></span> 、 <span class="t-c"><span class="mw-geshi c source-c"><a href="c-numeric-complex-ctanh.html"><span class="kw815">ctanhl</span></a></span></span> ）。</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>arg</td>
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<td>-</td>
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<td>表示双曲角的浮点值</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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若不出现错误，则返回 <code>arg</code> 的双曲正切（ <span class="texhtml" style="white-space: nowrap;">tanh(arg)</span> 或 <span class="texhtml" style="white-space: nowrap;"><span class="t-mfrac"></span></span>
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<table>
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<td>e<span class="t-su">arg<br /></span>-e<span class="t-su">-arg<br /></span></td>
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<tr>
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<td>e<span class="t-su">arg<br /></span>+e<span class="t-su">-arg<br /></span></td>
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</tr>
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</table>
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）。
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<p>若发生下溢所致的错误，则返回（舍入后的）正确结果。</p>
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<h3><span class="mw-headline" id=".E9.94.99.E8.AF.AF.E5.A4.84.E7.90.86">错误处理</span></h3>
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<p>报告 <a href="c-numeric-math-math_errhandling.html">math_errhandling</a> 中指定的错误。</p>
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<p>若实现支持 IEEE 浮点算术（ IEC 60559 ），则</p>
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<ul>
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<li>若参数为 ±0 ，则返回 ±0</li>
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<li>若参数为 ±∞ ，则返回 ±1</li>
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<li>若参数为 NaN ，则返回 NaN</li>
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</ul>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p><a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/tanh.html">POSIX 指定</a>在下溢的情况中，返回不修改的 <code>arg</code> ，而且若不支持这么做，则返回不大于 DBL_MIN 、 FLT_MIN 和 LDBL_MIN 的实现定义值。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <math.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"tanh(1) = %f<span class="es1">\n</span>tanh(-1) = %f<span class="es1">\n</span>"</span>, tanh<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span>, tanh<span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"tanh(0.1)*sinh(0.2)-cosh(0.2) = %f<span class="es1">\n</span>"</span>, tanh<span class="br0">(</span><span class="nu16">0.1</span><span class="br0">)</span> <span class="sy2">*</span> <a href="c-numeric-math-sinh.html"><span class="kw676">sinh</span></a><span class="br0">(</span><span class="nu16">0.2</span><span class="br0">)</span> <span class="sy2">-</span> <a href="c-numeric-math-cosh.html"><span class="kw677">cosh</span></a><span class="br0">(</span><span class="nu16">0.2</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 特殊值</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"tanh(+0) = %f<span class="es1">\n</span>tanh(-0) = %f<span class="es1">\n</span>"</span>, tanh<span class="br0">(</span><span class="nu16">0.0</span><span class="br0">)</span>, tanh<span class="br0">(</span><span class="sy2">-</span><span class="nu16">0.0</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">tanh(1) = 0.761594
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tanh(-1) = -0.761594
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tanh(0.1)*sinh(0.2)-cosh(0.2) = -1.000000
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tanh(+0) = 0.000000
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tanh(-0) = -0.000000</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.12.5.6 The tanh functions (p: 242)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>7.25 Type-generic math <tgmath.h> (p: 373-375)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>F.10.2.6 The tanh functions (p: 520)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.12.5.6 The tanh functions (p: 222-223)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>7.22 Type-generic math <tgmath.h> (p: 335-337)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>F.9.2.6 The tanh functions (p: 457)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>4.5.3.3 The tanh function</li>
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</ul>
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</dd>
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</dl>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-numeric-math-sinh.html"><span class="t-lines"><span>sinh</span><span>sinhf</span><span>sinhl</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>计算双曲正弦（ <span class="mjax" style="display:none">\({\small\sinh{x} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">sinh(x)</span> ）<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-numeric-math-cosh.html"><span class="t-lines"><span>cosh</span><span>coshf</span><span>coshl</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>计算双曲余弦（ <span class="mjax" style="display:none">\({\small\cosh{x} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">cosh(x)</span> ）<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-numeric-math-atanh.html"><span class="t-lines"><span>atanh</span><span>atanhf</span><span>atanhl</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>计算反双曲正切（ <span class="mjax" style="display:none">\({\small\operatorname{artanh}{x} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">artanh(x)</span> ）<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-numeric-complex-ctanh.html"><span class="t-lines"><span>ctanh</span><span>ctanhf</span><span>ctanhl</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>计算复数双曲正切<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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</div>
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</div>
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<div class="visualClear"></div>
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