计算八边形面积的程序

正八边形是具有相同长度的边和相同尺寸的内角的闭合图形。它具有8条反射对称性和8次旋转对称性的线。正八边形的每个顶点的内角为135°。中心角为45°。
特性 ：

Convex polygon, Equilateral polygon, Isogonal figure, Isotoxal figure, Cyclic.

公式 ：

Area : 2 × (side length)² × (1+sqrt(2))

例子 ：

Input : side = 3
Output : Area of Regular Octagon = 43.4558

Input : side = 4
Output : Area of Regular Octagon = 77.2548

C++

// CPP program to find area of octagon
#include 
using namespace std;
 
// Utility function
double areaOctagon(double side)
{
    return (float)(2 * (1 + sqrt(2)) *
                   side * side);
}
 
// Driver Code
int main()
{
    double side = 4;
    cout << "Area of Regular Octagon = "
         << areaOctagon(side) << endl;
    return 0;
}

Java

// Java Program to find
// area of Octagon.
import java.io.*;
 
class GFG
{  
    // utility function
    static double areaOctagon(double side)
    {
    return (float)(2 * (1 + Math.sqrt(2))
                          * side * side);
    }
     
    // driver code
    public static void main(String arg[])
    {
        double side = 4;
        System.out.print("Area of Regular Octagon = " 
                          + areaOctagon(side));
    }
}
 
// This code is contributed by Anant Agarwal.

Python3

# Python3 program to
# find area of octagon
 
import math
 
# Utility function
def areaOctagon(side):
    return (2 * (1 + (math.sqrt(2))) * side * side)
 
# Driver function
side = 4
print("Area of Regular Octagon =",
       round(areaOctagon(side), 4))
 
# This code is contributed
# by Azkia Anam.

C#

// C# Program to find
// area of Octagon.
using System;
 
class GFG
{
    // utility function
    static double areaOctagon(double side)
    {
    return (float)(2 * (1 + Math.Sqrt(2))
                        * side * side);
    }
     
    // Driver code
    public static void Main()
    {
        double side = 4;
        Console.WriteLine("Area of Regular Octagon = "
                          + areaOctagon(side));
    }
}
 
// This code is contributed by vt_m.

Javascript

 
// Javascript program to find area of octagon
 
// Utility function
function areaOctagon(side)
{
    return (2 * (1 + Math.sqrt(2)) *
                side * side);
}
 
// Driver Code
    let side = 4;
    document.write("Area of Regular Octagon = "
        + areaOctagon(side) + "<br>");
 
// This code is contributed by Mayank Tyagi

输出 ：

Area of Regular Octagon = 77.2548