正十边形的对角线

给定整数a为正十边形的边，任务是查找并打印其对角线的长度。

例子：

Input: a = 5 
Output: 9.51
Input: a = 9 
Output: 17.118 
 

方法：我们知道多边形的内角总和= (n – 2)* 180 ，其中， n为否。多边形中的边数。
因此，十边形的内角之和= 8 * 180 = 1440 ，每个内角将为144 。
现在，我们必须找到BC = 2 * x 。如果在BC上绘制垂直AO ，我们将看到BO和OC中的垂直二等分BC ，因为三角形AOB和AOC彼此相等。
因此，在三角形AOB中， sin(72)= x / a即x = 0.951 * a
因此，对角线长度将为2 * x，即1.902 * a 。
下面是上述方法的实现：

C++

// C++ program to find the diagonal
// of a regular decagon
#include 
using namespace std;
 
// Function to return the diagonal
// of a regular decagon
float decdiagonal(float a)
{
 
    // Side cannot be negative
    if (a < 0)
        return -1;
 
    // Length of the diagonal
    float d = 1.902 * a;
    return d;
}
 
// Driver code
int main()
{
    float a = 9;
    cout << decdiagonal(a) << endl;
    return 0;
}

Java

// Java program to find the diagonal of a regular decdiagonal
import java.util.*;
import java.lang.*;
import java.io.*;
 
public class GFG {
 
    // Function to return the diagonal of a regular decdiagonal
    static double decdiagonal(double a)
    {
 
//side cannot be negative
        if(a<0)
        return -1;
 
        // length of the diagonal
        double d=1.902*a;
         
        return d;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int a = 9;
        System.out.println(decdiagonal(a));
    }
}

Python3

# Python3 program to find the diagonal
# of a regular decagon
 
# Function to return the diagonal
# of a regular decagon
def decdiagonal(a) :
 
    # Side cannot be negative
    if (a < 0) :
        return -1
 
    # Length of the diagonal
    d = 1.902 * a
    return d
 
# Driver code
if __name__ == "__main__" :
 
    a = 9
    print(decdiagonal(a))
     
# This code is contributed by Ryuga

C#

// C# program to find the diagonal of a regular decdiagonal
using System;
 
public class GFG {
 
    // Function to return the diagonal of a regular decdiagonal
    static double decdiagonal(double a)
    {
 
//side cannot be negative
        if(a<0)
        return -1;
 
        // length of the diagonal
        double d=1.902*a;
         
        return d;
    }
 
    // Driver code
    public static void Main()
    {
        int a = 9;
        Console.WriteLine(decdiagonal(a));
    }
}
// This code is contributed by anuj_67..

Javascript

// javascript program to find the diagonal of a regular decdiagonal
 
// Function to return the diagonal of a regular decdiagonal
function decdiagonal(a)
{
 
// side cannot be negative
if(a < 0)
return -1;
 
// length of the diagonal
var d = 1.902*a;
 
return d;
}
 
// Driver code
 
var a = 9;
document.write(decdiagonal(a));
 
// This code contributed by Princi Singh

输出：

17.118