# atanh() function in C++ STL

The atanh() function returns the arc hyperbolic tangent or the inverse hyperbolic tangent of an angle given in radians. It is an inbuilt function in C++ STL.

The syntax of the atanh() function is given as follows.

atanh(var)

As can be seen from the syntax, the function atanh() accepts a parameter var of data type float, double or long double. The value of this parameter should be between -1 and 1. It returns the arc hyperbolic tangent of var.

A program that demonstrates atanh() in C++ is given as follows.

## Example

Live Demo

#include <iostream>
#include <cmath>
using namespace std;
int main() {
double d = 0.5, ans;
ans = atanh(d);
cout << "atanh("<< d <<") = " << ans << endl;
return 0;
}

## Output

atanh(0.5) = 0.549306

In the above program, first the variable d is initialized. Then arc hyperbolic tangent of d is found using atanh() and stored in ans. Finally the value of ans is displayed. This is demonstrated by the following code snippet.

double d = 0.5, ans;
ans = atanh(d);
cout << "atanh("<< d <<") = " << ans << endl;

The result obtained by using the atanh() function can be converted into degrees and displayed. A program to demonstrate this is as follows.

## Example

Live Demo

#include <iostream>
#include <cmath>
using namespace std;
int main() {
double d = 0.5, ans;
ans = atanh(d);
ans = ans*180/3.14159;
cout << "atanh("<<d <<") = " << ans << endl;
return 0;
}

## Output

atanh(0.5) = 31.473

In the above program, the arc hyperbolic tangent is obtained using atanh(). Then this value is converted into degrees. Finally, the output is displayed. This is demonstrated by the following code snippet.

double d = 0.5, ans;
ans = atanh(d);
ans = ans*180/3.14159;
cout << "atanh("<< d <<") = " << ans << endl;