php man page for atan

ATAN(3) 								 1								   ATAN(3)

atan - Arc tangent

SYNOPSIS
       float atan (float  $arg)

DESCRIPTION
	Returns  the  arc  tangent of $arg in radians. atan(3) is the complementary function of tan(3), which means that a==tan(atan(a)) for every
       value of a that is within atan(3)'s range.

PARAMETERS
	      o $arg
		- The argument to process

RETURN VALUES
	The arc tangent of $arg in radians.

SEE ALSO
       tan(3), atanh(3), asin(3), acos(3).

PHP Documentation Group 														   ATAN(3)