<!DOCTYPE html>
<html>
<body>

<?php
echo(atan2(0.50,0.50) . " ");
echo(atan2(-0.50,-0.50) . " ");
echo(atan2(5,5) . " ");
echo(atan2(10,20) . " ");
echo(atan2(-5,-5) . " ");
echo(atan2(-10,10));
?>

</body>
</html>