sqrt.xml

<?xml version="1.0" encoding="utf-8"?>
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<!-- EN-Revision: 61374bbe228e8e9c55a24aba59a1e2bb2a871148 Maintainer: dallas Status: ready -->
<!-- CREDITS: mowangjuanzi -->
<refentry xml:id="function.sqrt" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>sqrt</refname>
  <refpurpose>平方根</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>float</type><methodname>sqrt</methodname>
   <methodparam><type>float</type><parameter>num</parameter></methodparam>
  </methodsynopsis>
  <para>
   返回 <parameter>num</parameter> 的平方根。
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>num</parameter></term>
     <listitem>
      <para>
       要处理的参数
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   返回 <parameter>num</parameter> 的平方根，负数时返回 <constant>NAN</constant>。
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>sqrt</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php
// 精度取决于精度指令
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>pow</function></member>
    <member><constant>M_SQRTPI</constant>——<code>sqrt(pi)</code></member>
    <member><constant>M_2_SQRTPI</constant>——<code>2/sqrt(pi)</code></member>
    <member><constant>M_SQRT2</constant>——<code>sqrt(2)</code></member>
    <member><constant>M_SQRT3</constant>——<code>sqrt(3)</code></member>
    <member><constant>M_SQRT1_2</constant>——<code>1/sqrt(2)</code></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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