149 lines
9.9 KiB
HTML
149 lines
9.9 KiB
HTML
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<title>std::cos(std::complex)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>cos<span style="font-size:0.7em; line-height:130%">(std::complex)</span></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-complex.html">complex</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-complex.html"><complex></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T <span class="sy1">></span><br />
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complex<span class="sy1"><</span>T<span class="sy1">></span> cos<span class="br0">(</span> <span class="kw4">const</span> complex<span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> z <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>计算复数值 <code>z</code> 的复余弦。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>z</td>
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<td>-</td>
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<td>复数值</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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<p>若不出现错误，则返回 <code>z</code> 的复余弦。</p>
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<p>如同以 <code><a href="cpp-numeric-complex-cosh.html">std::cosh</a>(i*z)</code> 实现运算一般处理错误和特殊情况，其中 <code>i</code> 为虚数单位。</p>
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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>余弦在复平面上是整函数，而且无分支切割。</p>
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余弦的数学定义是 <span class="texhtml" style="white-space: nowrap;">cos z = <span class="t-mfrac"></span></span>
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<td>e<span class="t-su">iz<br /></span>+e<span class="t-su">-iz<br /></span></td>
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<td>2</td>
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。
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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="co2">#include <complex></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="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <a href="cpp-io-manip-fixed.html"><span class="kw1784">std::<span class="me2">fixed</span></span></a><span class="sy4">;</span>
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<a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> z<span class="br0">(</span><span class="nu0">1</span>, <span class="nu0">0</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 表现类似沿实轴的实余弦</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"cos"</span> <span class="sy1"><<</span> z <span class="sy1"><<</span> <span class="st0">" = "</span> <span class="sy1"><<</span> <a href="cpp-numeric-math-cos.html"><span class="kw1334">std::<span class="me2">cos</span></span></a><span class="br0">(</span>z<span class="br0">)</span>
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<span class="sy1"><<</span> <span class="st0">" ( cos(1) = "</span> <span class="sy1"><<</span> <a href="cpp-numeric-math-cos.html"><span class="kw1334">std::<span class="me2">cos</span></span></a><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><span class="sy4">;</span>
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<a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> z2<span class="br0">(</span><span class="nu0">0</span>, <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 表现类似沿虚轴的实 cosh</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"cos"</span> <span class="sy1"><<</span> z2 <span class="sy1"><<</span> <span class="st0">" = "</span> <span class="sy1"><<</span> <a href="cpp-numeric-math-cos.html"><span class="kw1334">std::<span class="me2">cos</span></span></a><span class="br0">(</span>z2<span class="br0">)</span>
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<span class="sy1"><<</span> <span class="st0">" (cosh(1) = "</span> <span class="sy1"><<</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="nu0">1</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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<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">cos(1.000000,0.000000) = (0.540302,-0.000000) ( cos(1) = 0.540302)
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cos(0.000000,1.000000) = (1.543081,-0.000000) (cosh(1) = 1.543081)</pre></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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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-sin.html"><span class="t-lines"><span>sin<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>计算复数的正弦（ <span class="mjax" style="display:none">\({\small\sin{z} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">sin(z)</span> ）<br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-tan.html"><span class="t-lines"><span>tan<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>计算复数的正切（ <span class="mjax" style="display:none">\({\small\tan{z} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">tan(z)</span> ）<br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-acos.html"><span class="t-lines"><span>acos<span class="t-dsc-small">(std::complex)</span></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></div>
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</div>
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<td>计算复数的反余弦（ <span class="mjax" style="display:none">\({\small\arccos{z} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">arccos(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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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-math-cos.html"><span class="t-lines"><span>cos</span><span>cosf</span><span>cosl</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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<td>计算余弦（ <span class="mjax" style="display:none">\({\small\cos{x} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">cos(x)</span> ）<br />
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<span class="t-mark">(函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-valarray-cos.html"><span class="t-lines"><span>cos<span class="t-dsc-small">(std::valarray)</span></span></span></a></div>
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<td>应用函数 <span class="t-lc"><a href="cpp-numeric-math-cos.html">std::cos</a></span> 到 valarray 的每个元素<br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="visualClear"></div>
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