acosh, acoshf, acoshl - inverse hyperbolic cosine function

#include <math.h>
 I double acosh(double  x );

I float acoshf(float  x );

I long double acoshl(long double  x );
 

Link with -lm.

The R 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, R acosh () returns not-a-number (NaN) and errno is set.

EDOM

SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double variants are C99 requirements.

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