|ACOS(3P)||POSIX Programmer's Manual||ACOS(3P)|
double acos(double x); float acosf(float x); long double acosl(long double x);
These functions shall compute the principal value of the arc cosine 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.
For finite values of x not in the range [-1,1], a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.
If x is NaN, a NaN shall be returned.
If x is +1, +0 shall be returned.
If x is ±Inf, a domain error shall occur, and a NaN shall be returned.
- Domain Error
- The x argument is finite and is not in the range [-1,1], 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.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
|2017||IEEE/The Open Group|