# Library Function acosh in Math Class

## Library Function acosh of math.h Header File in C

On this page we will discuss about library function acosh in math class which is used in C.

The C header file math.h contains the standard math library functions that can be used for performing various mathematical operations. The acosh function returns the arc hyperbolic cosine of x in radians. ## Library Function acosh of math.h Header File

In C programming language the acosh function is included in math.h header file.

The acosh function takes input argument in the range of $(x\geq 1)$ and returns the inverse hyperbolic cosine of parameter x in radians.

### Declaration of acosh function

double acosh(double x)

We can find the inverse hyperbolic cosine of different data types like int, float or long double by using the cast operator which explicitly converts the data type to double as given below:
int x = 0;
double result;
result = acosh(double(x));


### Parameters of acosh function

The acosh function accepts a single input value which is greater than or equal to 1.

ParameterDescription
double valueThis value of double function is greater than or equal to 1$(x\geq 1)$.

### Return value of acosh function

The acosh function returns a value or a number which is greater than or equal to 0 in radians. The function returns NaN if the parameter passed to acosh function is less than 1.

ParameterReturn Value
$x\geq 1$It returns a number greater than or equal to 0 in radians
x>1 or x<-1NaN (not a number)

### Implementation of Library Function math.h acosh

#### Example 1:

The following code shows the use of acosh function with different parameters passed to the function.

Run
#include <stdio.h>
#include <math.h>

int main()
{
// constant PI is defined
const double PI =  3.1415926;
double y, return_value_of_function;

y =  6.8;
return_value_of_function = acosh(y);
printf("Value of acosh(%.2f) function = %.2lf in radians\n", y, return_value_of_function);

return_value_of_function = acosh(y)*180/PI;
printf("Value of acosh(%.2f) function = %.2lf in degrees\n", y, return_value_of_function);

// parameter not in range
y = 0.7;
return_value_of_function = acosh(y);
printf("Value of acosh(%.2f) function = %.2lf", y, return_value_of_function);

return 0;
}


#### Output:

Value of acosh(6.80) function = 2.60 in radians
Value of acosh(6.80) function = 149.23 in degrees
Value of acosh(0.70) function = -nan


#### Example 2:

The following code shows the use of acosh function when parameters such as INFINITY and DBL_MAX are passed to the function.

Run
#include <stdio.h>
#include <math.h>
#include <float.h>

int main()
{
double y, return_value_of_function;

// maximum representable finite floating-point number
y =  DBL_MAX;
return_value_of_function = acosh(y);
printf("Maximum value of acosh() function in radians = %.3lf\n", return_value_of_function);

// Infinity
y = INFINITY;
return_value_of_function = acosh(y);
printf("When infinity is passed to acosh() function, return_value = %.3lf\n", return_value_of_function);

return 0;
}


#### Output:

Maximum value of acosh() function in radians = 710.476
When infinity is passed to acosh() function, return_value = inf


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