|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.1‐2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, <math.h>
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|2013||IEEE/The Open Group|