php man page for expm1

EXPM1(3)								 1								  EXPM1(3)

expm1 - Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero

SYNOPSIS
       float expm1 (float  $arg)

DESCRIPTION
       expm1(3)  returns the equivalent to 'exp($arg) - 1' computed in a way that is accurate even if the value of $arg is near zero, a case where
       'exp ($arg) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal.

PARAMETERS
	      o $arg
		- The argument to process

RETURN VALUES
	'e' to the power of $arg minus one

CHANGELOG
       +--------+--------------------------------------------------+
       |Version |						   |
       |	|						   |
       |	|		    Description 		   |
       |	|						   |
       +--------+--------------------------------------------------+
       | 5.3.0	|						   |
       |	|						   |
       |	|  This function is now available on all platforms |
       |	|						   |
       +--------+--------------------------------------------------+
SEE ALSO
       log1p(3), exp(3).

PHP Documentation Group 														  EXPM1(3)