function
<cmath> <ctgmath>

acosh

     double acosh  (double x);
      float acoshf (float x);
long double acoshl (long double x);

     double acosh (double x);
      float acosh (float x);
long double acosh (long double x);
     double acosh (T x);           // additional overloads for integral types
Compute arc hyperbolic cosine
Returns the nonnegative arc hyperbolic cosine of x, expressed in radians.

The arc hyperbolic cosine is the inverse operation of the hyperbolic cosine.

Header <tgmath.h> provides a type-generic macro version of this function.
Additional overloads are provided in this header (<cmath>) for the integral types: These overloads effectively cast x to a double before calculations (defined for T being any integral type).

This function is also overloaded in <complex> (see complex acosh).

Parameters

x
Value whose arc hyperbolic cosine is computed.
If the argument is less than 1, a domain error occurs.

Return Value

Nonnegative arc hyperbolic cosine of x, in the interval [0,+INFINITY] radians.
Note that the negative of this value is also a valid arc hyperbolic cosine of x One radian is equivalent to 180/PI degrees.

If a domain error occurs:
- And math_errhandling has MATH_ERRNO set: the global variable errno is set to EDOM.
- And math_errhandling has MATH_ERREXCEPT set: FE_INVALID is raised.

Example

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/* acosh example */
#include <stdio.h>      /* printf */
#include <math.h>       /* acosh, exp, sinh */

int main ()
{
  double param, result;
  param = exp(2) - sinh(2);
  result = acosh(param) ;
  printf ("The arc hyperbolic cosine of %f is %f radians.\n", param, result);
  return 0;
}


Output:

The arc hyperbolic cosine of 3.762196 is 2.000000 radians.

See also

cosh
Compute hyperbolic cosine (function )
asinh
Compute arc hyperbolic sine (function )

C++