asin

       #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():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       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.

ERRORS
       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
       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.
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