acosh, acoshf, acoshl − inverse hyperbolic cosine function

#include <math.h>

double acosh(double x);

float acoshf(float x);

long double acoshl(long double x);

The acosh() function calculates the inverse hyperbolic cosine of x; that is the value whose hyperbolic cosine is x. If x is less than 1.0, acosh() returns not-a-number (NaN) and errno is set.

EDOM

x is out of range.

SVID 3, POSIX, BSD 4.3, ISO 9899. The float and long double variants are C99 requirements.

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