'\" t
.\" Copyright, The contributors to the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH asin 3 2025-05-06 "Linux man-pages 6.14"
.SH NAME
asin, asinf, asinl \- arc sine function
.SH LIBRARY
Math library
.RI ( libm ,\~ \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double asin(double " x );
.BI "float asinf(float " x );
.BI "long double asinl(long double " x );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR asinf (),
.BR asinl ():
.nf
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions calculate the principal value of the arc sine of
.IR x ;
that is the value whose sine is
.IR x .
.SH RETURN VALUE
On success, these functions return the principal value of the arc sine of
.I x
in radians; the return value is in the range [\-pi/2,\ pi/2].
.P
If
.I x
is a NaN, a NaN is returned.
.P
If
.I x
is +0 (\-0),
+0 (\-0) is returned.
.P
If
.I x
is outside the range [\-1,\ 1],
a domain error occurs,
and a NaN is returned.
.\"
.\" POSIX.1-2001 documents an optional range error for subnormal x;
.\" glibc 2.8 does not do this.
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.P
The following errors can occur:
.TP
Domain error: \f[I]x\f[] is outside the range [\-1,\ 1]
.I errno
is set to
.BR EDOM .
An invalid floating-point exception
.RB ( FE_INVALID )
is raised.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR asin (),
.BR asinf (),
.BR asinl ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR acos (3),
.BR atan (3),
.BR atan2 (3),
.BR casin (3),
.BR cos (3),
.BR sin (3),
.BR tan (3)