211 lines
13 KiB
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211 lines
13 KiB
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<title>std::tanh, std::tanhf, std::tanhl</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_math_tanh skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>tanh, <span style="font-size:0.7em; line-height:130%">std::</span>tanhf, <span style="font-size:0.7em; line-height:130%">std::</span>tanhl</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-numeric.html">numeric</a>‎ | <a href="cpp-numeric-math.html">math</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-cmath.html"><cmath></a></code></div>
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<td></td>
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<td></td>
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<td rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span> tanh <span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><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><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><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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<td rowspan="142">(3)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span> tanh <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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<div><span class="mw-geshi cpp source-cpp"><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><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span> tanh <span class="br0">(</span> IntegralType arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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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> 接受任何<a href="cpp-types-is_integral.html">整数类型</a>参数的重载集或函数模板。等价于 2) （将参数转型为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></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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<td>arg</td>
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<td>-</td>
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<td>浮点或<a href="cpp-types-is_integral.html">整数类型</a>值</td>
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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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<td>e<span class="t-su">arg<br /></span>-e<span class="t-su">-arg<br /></span></td>
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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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）。
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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 <span class="t-lc"><a href="cpp-numeric-math-math_errhandling.html">math_errhandling</a></span> 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 class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <cmath></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"tanh(1) = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">tanh</span><span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"tanh(-1) = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">tanh</span><span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"tanh(0.1)*sinh(0.2)-cosh(0.2) = "</span>
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<span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">tanh</span><span class="br0">(</span><span class="nu16">0.1</span><span class="br0">)</span> <span class="sy2">*</span> <a href="cpp-numeric-math-sinh.html"><span class="kw1340">std::<span class="me2">sinh</span></span></a><span class="br0">(</span><span class="nu16">0.2</span><span class="br0">)</span> <span class="sy2">-</span> <a href="cpp-numeric-math-cosh.html"><span class="kw1341">std::<span class="me2">cosh</span></span></a><span class="br0">(</span><span class="nu16">0.2</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="co1">// 特殊值</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"tanh(+0) = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">tanh</span><span class="br0">(</span><span class="sy2">+</span><span class="nu16">0.0</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"tanh(-0) = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">tanh</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">0.0</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</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
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tanh(+0) = 0
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tanh(-0) = -0</pre></div>
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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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<div class="t-dsc-member-div">
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<div><a href="cpp-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-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</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 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="cpp-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-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</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 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="cpp-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-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-tanh.html"><span class="t-lines"><span>tanh<span class="t-dsc-small">(std::complex)</span></span></span></a></div>
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</div>
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</td>
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<td>计算复数的双曲正切（ <span class="mjax" style="display:none">\({\small\tanh{z} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">tanh(z)</span> ）<br />
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<span class="t-mark">(函数模板)</span></td>
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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="cpp-numeric-valarray-tanh.html"><span class="t-lines"><span>tanh<span class="t-dsc-small">(std::valarray)</span></span></span></a></div>
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</div>
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</td>
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<td>在 valarray 的每个元素上调用 <span class="t-lc"><strong class="selflink">std::tanh</strong></span> 函数<br />
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<span class="t-mark">(函数模板)</span></td>
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</table>
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</div>
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<div class="visualClear"></div>
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