php man page for sqrt

SQRT(3) 								 1								   SQRT(3)

sqrt - Square root

SYNOPSIS
       float sqrt (float  $arg)

DESCRIPTION
	Returns the square root of $arg.

PARAMETERS
	      o $arg
		- The argument to process

RETURN VALUES
	The square root of $arg or the special value NAN for negative numbers.

EXAMPLES
       Example #1

	      sqrt(3) example

	      <?php
	      // Precision depends on your precision directive
	      echo sqrt(9); // 3
	      echo sqrt(10); // 3.16227766 ...
	      ?>

SEE ALSO
       pow(3).

PHP Documentation Group 														   SQRT(3)