ACOSH(3)

NAME
acosh - inverse hyperbolic cosine function

SYNOPSIS
#include <math.h>
double
acosh(double x);
long double
acoshl(long double x);
float
acoshf(float x);

DESCRIPTION
The acosh() function computes the principle value of the inverse hyperbolic cosine of x. The result is in the range [0, +infinity].

SPECIAL VALUES
acosh(1) returns +0.

acosh(x) returns a NAN and raises the "invalid" floating-point exception for x < 1.

acosh(+infinity) returns +infinity.

SEE ALSO
asinh(3), atanh(3), exp(3), math(3)

STANDARDS
The acosh() function conforms to ISO/IEC 9899:1999(E).

HISTORY
The acosh() and acoshf() function appeared in 4.3BSD.