# man pages section 3: Extended Library Functions, Volume 2

Updated: Thursday, June 13, 2019

## asinl(3M)

### Name

asin, asinf, asinl - arc sine function

### Synopsis

```c99 [ flag... ] file... –lm [ library... ]
#include <math.h>

double asin(double x);```
`float asinf(float x);`
`long double asinl(long double x);`

### Description

These functions compute the principal value of the arc sine of their argument x. The value of x should be in the range [−1,1].

### Return Values

Upon successful completion, these functions return the arc sine of x in the range [−π/2, π/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, NaN is returned.

If x is ±0, x is returned.

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

For exceptional cases, matherr(3M) tabulates the values to be returned by asin() as specified by SVID3 and XPG3.

### Errors

These functions will fail if:

Domain Error

The x argument is finite and not in the range [−1,1], or is ±Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised.

The asin() function sets errno to EDOM if x is not ±Inf or NaN and is not in the range [−1,1].

### Usage

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling asin(). On return, if errno is non-zero, an error has occurred. The asinf() and asinl() functions do not set errno.

### Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Availability
system/library/math
MT-Level
MT-Safe
Standard