正五边形的对角线

给定整数a ，它是规则五边形的边，任务是查找并打印其对角线的长度。

例子：

Input: a = 6 
Output: 7.32
Input: a = 9 
Output: 10.98 
 

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，五边形的内角之和= 3 * 180 = 540 ，每个内角将为108 。
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(54)= x / a即x = 0.61 * a
因此，对角线长度将为2 * x，即1.22 * a 。
下面是上述方法的实现：

C++

// C++ Program to find the diagonal
// of a regular pentagon
#include 
using namespace std;
 
// Function to find the diagonal
// of a regular pentagon
float pentdiagonal(float a)
{
 
    // Side cannot be negative
    if (a < 0)
        return -1;
 
    // Length of the diagonal
    float d = 1.22 * a;
    return d;
}
 
// Driver code
int main()
{
    float a = 6;
    cout << pentdiagonal(a) << endl;
    return 0;
}

Java

// Java Program to find the diagonal
// of a regular pentagon
class GFG
{
     
// Function to find the diagonal
// of a regular pentagon
static double pentdiagonal(double a)
{
 
    // Side cannot be negative
    if (a < 0)
        return -1;
 
    // Length of the diagonal
    double d = 1.22 * a;
    return d;
}
 
// Driver code
static public void main (String args[])
{
    double a = 6;
    System.out.println(pentdiagonal(a));
}
}
 
// This code is contributed
// by Akanksha Rai

Python3

# Python3 Program to find the diagonal
# of a regular pentagon
 
# Function to find the diagonal
# of a regular pentagon
def pentdiagonal(a) :
 
    # Side cannot be negative
    if (a < 0) :
        return -1
 
    # Length of the diagonal
    d = 1.22 * a
    return d
 
# Driver code
if __name__ == "__main__" :
 
    a = 6
    print(pentdiagonal(a))
 
# This code is contributed by Ryuga

C#

// C# Program to find the diagonal
// of a regular pentagon
using System;
 
public class GFG{
     
// Function to find the diagonal
// of a regular pentagon
static double pentdiagonal(double a)
{
 
    // Side cannot be negative
    if (a < 0)
        return -1;
 
    // Length of the diagonal
    double d = 1.22 * a;
    return d;
}
 
// Driver code
    static public void Main (){
    double a = 6;
    Console.WriteLine(pentdiagonal(a));
    }
}

Javascript

    // Javascript Program to find the diagonal
    // of a regular pentagon
     
    // Function to find the diagonal 
    // of a regular pentagon
    function pentdiagonal(a)
    {
       
        // Side cannot be negative
        if (a < 0)
            return -1;
       
        // Length of the diagonal
        let d = 1.22 * a;
        return d;
    }
     
    let a = 6;
    document.write(pentdiagonal(a));
     

输出：

7.32