Arc hyperbolic cosine

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double __far acosh(double x); (C99)

[Return value]

Returns the arc hyperbolic cosine of x.

If x is smaller than 1, returns a Not-a-Number (NaN) and sets macro EDOM to global variable errno.

[Description]

This function calculates the arc hyperbolic cosine of x. Specify the angle in radian.