NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO |
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acos(3) Library Functions Manual acos(3)
acos, acosf, acosl - arc cosine function
Math library (libm, -lm)
#include <math.h> double acos(double x); float acosf(float x); long double acosl(long double x); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): acosf(), acosl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions calculate the arc cosine of x; that is the value whose cosine is x.
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.
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.
For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │acos(), acosf(), acosl() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
C99, POSIX.1-2001. The variant returning double also conforms to C89, SVr4, 4.3BSD.
asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)
Linux man-pages 6.04 2023-03-30 acos(3)
Pages that refer to this page: asin(3), atan2(3), atan(3), cos(3), sin(3), tan(3)