NAMEacos, acosf, acosl - arc cosine function
SYNOPSIS#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)): acosf(), acosl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99
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. If x is outside the range [-1, 1], 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 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at //www.kernel.org/doc/man-pages/. 2010-09-20 ACOSF(3)