asin, asinf, asinl - arc sine function
double asin(double x);
float asinf(float x);
long double asinl(long double x);
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.
These functions shall compute the principal value of the arc sine of their argument x. The value of x should be in the range [-1,1].
An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.
Upon successful completion, these functions shall return the arc sine of x, in the range [-/2,/2] radians.
For finite values of x not in the range [-1,1], a domain error shall occur, and [MX] either a NaN (if supported), or an implementation-defined value shall be returned.
[MX] If x is NaN, a NaN shall be returned.
If x is ±0, x shall be returned.
If x is ±Inf, a domain error shall occur, and a NaN shall be returned.
If x is subnormal, a range error may occur
[MXX] and x should be returned.
[MX] If x is not returned, asin(), asinf(), and asinl() shall return an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
These functions shall fail if:
- Domain Error
- The x argument is finite and is not in the range [-1,1], [MX] or is ±Inf.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.
These functions may fail if:
- Range Error
- [MX] The value of x is subnormal.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.
feclearexcept, fetestexcept, isnan, sin
XBD Treatment of Error Conditions for Mathematical Functions, <math.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.
The asinf() and asinl() functions are added for alignment with the ISO/IEC 9899:1999 standard.
The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.
IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0034  and XSH/TC1-2008/0035  are applied.
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