ACOSSection: Linux Programmer's Manual (3)
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NAMEacos, acosf, acosl - arc cosine function
#include <math.h> double acos(double x); float acosf(float x); long double acosl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTIONThe acos() function calculates the arc cosine of x; that is the value whose cosine is x.
RETURN VALUEOn 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.
ERRORSSee 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.
CONFORMING TOC99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
SEE ALSOasin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)
COLOPHONThis page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.