# asin(3M)

## NAME

asin - arc sine function

## SYNOPSIS

cc [ *flag* ... ] *file* ... -lm [ *library* ... ]
#include <math.h>
double asin(double *x*);

## DESCRIPTION

The asin() function computes the principal value of the arc
sine of *x*. The value of *x* should be in the range [-1,1].

## RETURN VALUES

Upon successful completion, asin() returns the arc sine of
*x*, in the range [-pi/2,pi/2] radians. If the value of *x* is
not in the range [-1,1] and is not **_**Inf or NaN, either 0.0
or NaN is returned and errno is set to EDOM.
If *x* is NaN, NaN is returned.
If *x* is **_**Inf, either 0.0 is returned and errno is set to
EDOM or NaN is returned and errno may be set to EDOM.
For exceptional cases, **matherr(3M)** tabulates the values to
be returned as dictated by Standards other than XPG4.

## ERRORS

The asin() function will fail if:
EDOM The value *x* is not **_**Inf or NaN and is not in the range
[-1,1].
The asin() function may fail if:
EDOM The value of *x* is **_**Inf.

## USAGE

An application wishing to check for error situations should
set errno to 0, then call asin(). If errno is non-zero on
return, or the return value is NaN, an error has occurred.

## ATTRIBUTES

See **attributes(5)** for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________*|*_____________________________*|*
| MT-Level | MT-Safe |
|_____________________________*|*_____________________________*|*

## SEE ALSO

**isnan(3M)**, **matherr(3M)**, **sin(3M)**, **attributes(5)**, **standards(5)**

Man(1) output converted with
man2html