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# Technical Reference: Base Operating System and Extensions, Volume 1

## asinf, asinl, or asin Subroutine

### Purpose

Computes the arc sine.

### Syntax

#include <math.h>
float asinf (x)
float x;
long double asinl (x)
long double x;
double asin (x)
double x;

### Description

The asinf, asinl, and asin subroutines compute the principal value of the arc sine of the x parameter. The value of x should
be in the range [-1,1].

An application wishing to check for error situations should set the errno global variable to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these subroutines. On return,
if errno is nonzero or fetestexcept(FE_INVALID
| FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has
occurred.

### Parameters

x |
Specifies the value to be computed. |

### Return Values

Upon successful completion, the asinf, asinl, and asin subroutines return the arc sine
of x, in the range [-pi /2, pi/2] radians.

For finite values of x not in the range [-1,1],
a domain error occurs, and a NaN is returned.

If x is NaN, a NaN is returned.

If x is 0, x is returned.

If x is ±Inf, a domain error occurs, and
a NaN is returned.

If x is subnormal, a range error may occur and x is returned.

### Related Information

The asinh, asinhf, or asinhl Subroutine.

math.h in AIX 5L Version 5.2 Files Reference.

Subroutines Overview in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.

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