Program to calculate area of Enneagon

Enneagon is a polygon with 9 sides and 9 internal angles. Enneagon is also known as Nonagon. A regular nonagon has an internal angle of 140 degrees each. Sum of interior angles of the nonagon is 1260 degree. 
The center of the circumcircle is also taken as the center of the regular Nonagon. 
The line segment drawn the perpendicular to a side of the Nonagon is called the Apothem and is represented by ‘a’.

 Area ≈ 6.1818 * s * s 
 where s is side length.

Examples: 

Input : 6
Output :Area of Regular Nonagon = 222.5448

Input : 8 
Output :Area of Regular Nonagon = 395.6352

C++

// CPP program to find area of a Enneagon
#include <iomanip>
#include <iostream>
#include <math.h>
using namespace std;

// Function to calculate area of nonagon
double Nonagon_Area(double s) {
  return (6.1818 * s * s);
}

// driver function
int main() {
  double s = 6; // Length of a side
  cout << "Area of Regular Nonagon = " << std::setprecision(7)
       << Nonagon_Area(s);
  return 0;
}

Java

// Java program to find area of a Enneagon
class Nonagon {

  // Function for calculating the area of the nonagon
  public static double Nonagon_Area(double s) {
    return ((6.1818 * (s * s)));
  }

  // driver code
  public static void main(String[] args) {
    double s = 6; // Length of a side
    System.out.print("Area of Regular Nonagon = " + Nonagon_Area(s));
  }
}

Python

# python program to find area of a Enneagon
length = 6
Nonagon_area = 6.1818 * (length ** 2)
print("Area of regular Nonagon is = ", Nonagon_area)

C#

// C# program to find area of a Hexagon
using System;

class Nonagon {

    // Function for calculating
    // the area of the nonagon
    public static double Nonagon_Area(double s)
    {
        return ((6.1818 * (s * s)));
    }

    // driver code
    public static void Main()
    {
        // Length of a side
        double s = 6;
        Console.WriteLine("Area of Regular Nonagon = " +
                                       Nonagon_Area(s));
    }
}

// This article is contributed by vt_m

PHP

<?php
// PHP program to find area of a Hexagon

    // Function to calculate
    // area of nonagon
    function Nonagon_Area($s)
    {
        return (6.1818 * $s * $s);
    }

// Driver Code

// Length of a side
$s = 6;

echo "Area of Regular Nonagon = "
    , Nonagon_Area($s);

// This code is contributed by anuj_67.
?>

Javascript

<script>

// javascript program to find area of a Enneagon


    // Function for calculating the area of the nonagon
    function Nonagon_Area(s) {
        return ((6.1818 * (s * s)));
    }

    // driver code

        var s = 6; // Length of a side
        document.write("Area of Regular Nonagon = " + Nonagon_Area(s));

// This code contributed by aashish1995

</script>

Output:

Area of Regular Nonagon = 222.5448

Time Complexity: O(1) 
Auxiliary Space: O(1)
Please suggest if someone has a better solution which is more efficient in terms of space and time.