Find length of Diagonal of Hexagon

Given a regular hexagon of side length a, the task is to find the length of it’s diagonal.
Examples: 

Input : a = 4
Output : 8

Input : a = 7
Output : 14

From the diagram, it is clear that the triangle ABC is an equilateral triangle, so 
AB = AC = BC = a.
also it is obvious, diagonal = 2*AC or 2*BC
So the length of diagonal of the hexagon = 2*a
Below is the implementation of the above approach: 

C++

// C++ Program to find the diagonal
// of the hexagon
#include <bits/stdc++.h>
using namespace std;

// Function to find the diagonal
// of the hexagon
float hexadiagonal(float a)
{
    // side cannot be negative
    if (a < 0)
        return -1;

    // diagonal of the hexagon
    return 2 * a;
}

// Driver code
int main()
{
    float a = 4;

    cout << hexadiagonal(a) << endl;

    return 0;
}

C

// C Program to find the diagonal
// of the hexagon
#include <stdio.h>

// Function to find the diagonal
// of the hexagon
float hexadiagonal(float a)
{
    // side cannot be negative
    if (a < 0)
        return -1;

    // diagonal of the hexagon
    return 2 * a;
}

// Driver code
int main()
{
    float a = 4;
    printf("%f\n",hexadiagonal(a));
    return 0;
}

Java

// Java Program to find the diagonal
// of the hexagon

import java.io.*;

class GFG {

// Function to find the diagonal
// of the hexagon
static float hexadiagonal(float a)
{
    // side cannot be negative
    if (a < 0)
        return -1;

    // diagonal of the hexagon
    return 2 * a;
}

// Driver code


    public static void main (String[] args) {
            float a = 4;

    System.out.print( hexadiagonal(a));
}
}

// This code is contributed
// by shs

Python3

# Python3 Program to find the diagonal
# of the hexagon

# Function to find the diagonal
# of the hexagon
def hexadiagonal(a):

    # side cannot be negative
    if (a < 0):
        return -1

    # diagonal of the hexagon
    return 2 * a


# Driver code
if __name__=='__main__':
    a = 4
    print(hexadiagonal(a))

# This code is contributed by
# Shivi_Aggarwal

C#

// C# Program to find the diagonal
// of the hexagon
using System;

class GFG {

    // Function to find the diagonal
    // of the hexagon
    static float hexadiagonal(float a)
    {
        // side cannot be negative
        if (a < 0)
            return -1;

        // diagonal of the hexagon
        return 2 * a;
    }

// Driver code
public static void Main()
{
   float a = 4;
   Console.WriteLine( hexadiagonal(a));
}
}

// This code is contributed
// by anuj_67..

PHP

<?php
// PHP Program to find the diagonal
// of the hexagon

// Function to find the diagonal
// of the hexagon
function hexadiagonal($a)
{
    // side cannot be negative
    if ($a < 0)
        return -1;

    // diagonal of the hexagon
    return 2 * $a;
}

// Driver code
    $a = 4;

    echo hexadiagonal($a);
    // This code is contributed
// by anuj_67..

?>

Javascript

<script>
// javascript Program to find the diagonal
// of the hexagon

// Function to find the diagonal
// of the hexagon
function hexadiagonal(a)
{

    // side cannot be negative
    if (a < 0)
        return -1;

    // diagonal of the hexagon
    return 2 * a;
}

// Driver code

var a = 4;
document.write( hexadiagonal(a));

// This code is contributed by 29AjayKumar
</script>

Output:

8

Time complexity: O(1), since there is no loop or recursion.

Auxiliary Space: O(1), since no extra space has been taken.