title: 'sqrt' is not a member of 'std'
body: <p>I compile my program in Linux - it has the following line:</p>
  <pre><code>std::sqrt((double)num);
  </code></pre>
  <p>On Windows, it is ok. However, on Linux, I get an error:</p>
  <blockquote>
  <p><code>sqrt</code> is not a member of <code>std</code></p>
  </blockquote>
  <p>I have already included <code>math.h</code>.</p>
  <p>What is the problem with that?</p>