## NAME

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),