php man page for acos

ACOS(3) 								 1								   ACOS(3)

acos - Arc cosine

SYNOPSIS
       float acos (float  $arg)

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

PARAMETERS
	      o $arg
		- The argument to process

RETURN VALUES
	The arc cosine of $arg in radians.

SEE ALSO
       cos(3), acosh(3), asin(3), atan(3).

PHP Documentation Group 														   ACOS(3)