| Domain error: x is outside the range [-1, 1] | errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised. |
NAME
acos, acosf, acosl - arc cosine function
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>double acos(double \nx\n);\n
\nfloat acosf(float \nx\n);\n
\nlong double acosl(long double \nx\n);acosf(), acosl():
\n
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION
These functions calculate the arc cosine of x; that is the value whose cosine is x.
RETURN VALUE
On success, these functions return the arc cosine of x in radians; the return value is in the range [0, pi].
If x is a NaN, a NaN is returned.
If x is +1, +0 is returned.
If x is positive infinity or negative infinity, a domain error occurs, and a NaN 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 |
| acos (), acosf (), acosl () | Thread safety | MT-Safe |
STANDARDS
C11, POSIX.1-2008.
HISTORY
C99, POSIX.1-2001.
The variant returning double also conforms to C89, SVr4, 4.3BSD.
SEE ALSO
asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)