# asin(3) — Linux manual page

```asin(3)                 Library Functions Manual                 asin(3)
```

## NAME         top

```       asin, asinf, asinl - arc sine function
```

## LIBRARY         top

```       Math library (libm, -lm)
```

## SYNOPSIS         top

```       #include <math.h>

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

Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):

asinf(), asinl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION         top

```       These functions calculate the principal value of the arc sine of
x; that is the value whose sine is x.
```

## RETURN VALUE         top

```       On success, these functions return the principal value of the arc
sine of x in radians; the return value is in the range
[-pi/2, pi/2].

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is outside the range [-1, 1], a domain error occurs, and a
NaN is returned.
```

## ERRORS         top

```       See math_error(7) for information on how to determine whether an
error has occurred when calling these functions.

The following errors can occur:

Domain error: x is outside the range [-1, 1]
errno is set to EDOM.  An invalid floating-point exception
(FE_INVALID) is raised.
```

## ATTRIBUTES         top

```       For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface                           │ Attribute     │ Value   │
├─────────────────────────────────────┼───────────────┼─────────┤
│ asin(), asinf(), asinl()            │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## STANDARDS         top

```       C11, POSIX.1-2008.
```

## HISTORY         top

```       C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89.
```

```       acos(3), atan(3), atan2(3), casin(3), cos(3), sin(3), tan(3)
```

## COLOPHON         top

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user-space interface documentation) project.  Information about
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⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
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⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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Linux man-pages 6.9.1          2024-05-02                        asin(3)
```