# acosh() function in C++ STL

### C++ STL Function : acosh()

The `acosh()` function uses a mathematical formula to calculate the inverse hyperbolic cosine of a number. This formula involves the use of exponential functions and involves the ratio of the sides of a right triangle in a hyperbolic coordinate system.In this section, we will discuss about library function acosh() in STL which is used in C++.The Standard Template Library(STL) is a set of complete data structures and functions which can be used in C++. ## Library Function acosh() in C++

In C++ programming language, the acosh function is included in standard template library.

The range of input argument which is passed to floor function is not limited here as it can be any value such as float or long double also.

### Declaration of acosh function

```acosh(data_type x)
```

### Parameters of acosh function

The acosh function accepts a single input argument  which is the hyperbolic angle and can be a double/float or long double value.

Parameter           Description
Hyperbolic angle          This value of the parameter can be of double / float /int or long double type.

### Return value of acosh function

The acosh function returns the inverse hyperbolic cosine value of the argument passed.

ParameterReturn Value
Inverse hyperbolic cosine of the argument passedIt returns the value in double / float / int or long double type.

### Implementation of STL Function acosh() in C++

#### Example 1:

The following code shows the use of acosh function.

Run

```#include<bits/stdc++.h>
using namespace std;
int main(){    double x = 50.0;    double result = acosh(x);    cout << "acosh(50.0) = " << result << " radians"<< endl;    cout << "acosh(50.0) = " << result * 180 / 3.141592<< " degrees" << endl;    return 0;}
```

#### Output:

```acosh(50.0) = 4.60507 radians
acosh(50.0) = 263.851 degrees
```

#### Example 2:

Run

```#include<bits/stdc++.h>
using namespace std;
int main(){    string x = "mno";    double result = acosh(x);    cout << "acosh(50.0) = " << result << " radians"<< endl;    cout << "acosh(50.0) = " << result * 180 / 3.141592<< " degrees" << endl;    return 0;}
```

#### Output:

```prog.cpp: In function ‘int main()’:prog.cpp:12:28: error: no matching function for call to ‘acosh(std::__cxx11::string&)’     double result = acosh(x);
```

#### Example 3:

Run

```#include<bits/stdc++.h>
using namespace std;
int main(){    double x = -50.0;    double result = acosh(x);    cout << "acosh(-50.0) = " << result << " radians"<< endl;    cout << "acosh(-50.0) = " << result * 180 / 3.141592<< " degrees" << endl;    return 0;}
```

#### Output:

```acosh(-50.0) = -nan radiansacosh(-50.0) = -nan degrees
```

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