asin man page

asin, asinf, asinl — arc sine function


#include <math.h>

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

Link with -lm.

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

asinf(), asinl():

   || /* Since glibc 2.19: */ _DEFAULT_SOURCE
   || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


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

Return Value

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.


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.


For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
asin(), asinf(), asinl() Thread safety MT-Safe

Conforming to

C99, POSIX.1-2001, POSIX.1-2008.

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

See Also

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


This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

acos(3), atan(3), atan2(3), cos(3), sin(3), tan(3).

The man pages asinf(3) and asinl(3) are aliases of asin(3).

2017-09-15 Linux Programmer's Manual