acosh, acoshf, acoshl − inverse hyperbolic cosine function
Math library (libm, −lm)
#include <math.h>
double
acosh(double x);
float acoshf(float x);
long double acoshl(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
acosh():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
acoshf(),
acoshl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions calculate the inverse hyperbolic cosine of x; that is the value whose hyperbolic cosine is x.
On success, these functions return the inverse hyperbolic cosine of x.
If x is a NaN, a NaN is returned.
If x is +1, +0 is returned.
If x is positive infinity, positive infinity is returned.
If x is less than 1, a domain error occurs, and the functions return a NaN.
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 less than 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). |
C11, POSIX.1-2008.
C99, POSIX.1-2001.
The variant returning double also conforms to SVr4, 4.3BSD.
asinh(3), atanh(3), cacosh(3), cosh(3), sinh(3), tanh(3)