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);
Compute area hyperbolic cosine
Returns the nonnegative area hyperbolic cosine of x.

The area 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 area hyperbolic cosine is computed.
If the argument is less than `1`, a domain error occurs.

### Return Value

Nonnegative area hyperbolic cosine of x, in the interval [0,+INFINITY].
Note that the negative of this value is also a valid area hyperbolic cosine of x
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

 ``123456789101112`` ``````/* acosh example */ #include /* printf */ #include /* acosh, exp, sinh */ int main () { double param, result; param = exp(2) - sinh(2); result = acosh(param) ; printf ("The area hyperbolic cosine of %f is %f radians.\n", param, result); return 0; }``````

Output:
 ``` The area hyperbolic cosine of 3.762196 is 2.000000 radians. ```