title: Mathf.Atan2 return incorrect result
body: <p>Sometimes when i move mouse (rotate camera around character), my character do rotation.
  But i do not have any character rotation by mouse.
  This is my rotation code, that depend only on keyboard input (I took this code from standard unity sample):</p>
  
  <pre><code>private void ConvertMoveInput()
  {
      Vector3 localMove = transform.InverseTransformDirection(_moveInput);
      _turnAmount = Mathf.Atan2(localMove.x, localMove.z);
      _forwardAmount = localMove.z;
  }
  </code></pre>
  
  <p>I figure out that sometimes when i move mouse Mathf.Atan2 return the number PI, even if two arguments are still equals to zero. How does this happens?</p>
  
  <p><img src="https://i.stack.imgur.com/uB96f.png" alt="Breakpoint"></p>
  
  <p>My demo project <a href="http://stasclick.zz.mu/Test1.html" rel="nofollow noreferrer">here</a>.</p>