asin - arc sine function

## SYNOPSIS

**#include** **<math.h>**
**double** **asin(double** *x***);**

## DESCRIPTION

The **asin()** function calculates the arc sine of *x*; that is
the value whose sine is *x*. If *x* falls outside the range
-1 to 1, **asin()** fails and *errno* is set.

## RETURN VALUE

The **asin()** function returns the arc sine in radians and
the value is mathematically defined to be between -PI/2
and PI/2 (inclusive).

## ERRORS

**EDOM** *x* is out of range.

## CONFORMING TO

SVID 3, POSIX, BSD 4.3, ISO 9899

## SEE ALSO

**acos(3)**, **atan(3)**, **atan2(3)**, **cos(3)**, **sin(3)**, **tan(3)**