php man page for asin

ASIN(3) 								 1								   ASIN(3)

asin - Arc sine

SYNOPSIS
       float asin (float  $arg)

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

PARAMETERS
	      o $arg
		- The argument to process

RETURN VALUES
	The arc sine of $arg in radians

SEE ALSO
       sin(3), asinh(3), acos(3), atan(3).

PHP Documentation Group 														   ASIN(3)