In trigonometry, the **`tangent` function** of a right-angled triangle is the ratio between the adjacent and opposite sides of a right triangle. 

The `tan` function in C++ works precisely like the tangent in trigonometry. The return value of the `tan` function is the tangent of an angle given in `radian`. 

To use the `tan` function, the `cmath` header file needs to be included in the program, as shown below:
```C++
#include <cmath>
```

# Parameters

The `tan` function takes one parameter, i.e., the angle. This parameter should be a numeric number and be in a `radian`.

# Return value

The `tan` function returns the value between -  $\infty$ and +  $\infty$ .

The function can have the return value of the following three types:
* float
* double
* long double

These types depend on the type of arguments the programmer gives to the functions. 

Figure 2 below shows the types of return types when different argument types are passed:

# Example

The code below shows how the `tan` function works in C++:

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
  // the value of x is in radians
  double x = 0.5;
  
  // result is in double
  cout << "tan(x) = " << tan(x) << endl;
  
  return 0;
}

How to use tan() in C++

Use the tan function in C++ by including the cmath header to calculate the tangent of an angle in radians. Parameters can be float, double, or long double.