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Name

acosh, acoshf, acoshl - inverse hyperbolic cosine function

Synopsis


#include <math.h>
double acosh(double x);
float acoshf(float x);
long double acoshl(long double x);
Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7) ):

acosh():

_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

acoshf(), acoshl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

Description

The acosh() function calculates the inverse hyperbolic cosine of x; that is the value whose hyperbolic cosine is x.

Return Value

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.

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 less than 1
errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

Conforming to

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.

See Also

asinh(3) , atanh(3) , cacosh(3) , cosh(3) , sinh(3) , tanh(3)

Colophon

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