Related Articles
Find the diagonal of the Cube
• Last Updated : 17 Mar, 2021

Given a side of the cube a. The task is to find the length of the diagonal of the cube. Examples:

Input : a = 3
Output : 5.19615
Input : a = 6
Output : 10.3923

Formula :

Length of diagonal of the cube = sqrt(3) * side

Proof :

Use Pythagorean Theorem,
In triangle CED,
CE2 = CD2 + DE2
l2 = a2 + a2 ———>(1)
In triangle CFE,
CF2 = CE2 + EF2
L2 = l2 + a2
use l2 value from equation(1),
L2 = a2 + a2 + a2
= 3*a2
L = sqrt(3) * a

## C++

 `// CPP program to find length``// of the diagonal of the cube``#include ``using` `namespace` `std;` `// Function to find length``// of diagonal of cube``float` `diagonal_length(``float` `a)``{``    ``float` `L;` `    ``// Formula to Find length``    ``// of diagonal of cube``    ``L = a * ``sqrt``(3);` `    ``return` `L;``}` `// Driver code``int` `main()``{` `    ``float` `a = 5;` `    ``// Function call``    ``cout << diagonal_length(a);` `    ``return` `0;``}`

## Java

 `// Java program to find length``// of the diagonal of the cube``class` `GFG``{``    ` `    ``// Function to find length``    ``// of diagonal of cube``    ``static` `float` `diagonal_length(``float` `a)``    ``{``        ``float` `L;``        ` `        ``// Formula to Find length``        ``// of diagonal of cube``        ``L = a * (``float``)Math.sqrt(``3``);``        ` `        ``return` `L;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``float` `a = ``5``;``        ` `        ``// Function call``        ``System.out.println(diagonal_length(a));``    ``}``}` `// This code is contributed by``// sanjeev2552`

## Python3

 `# Python3 program to find length``# of the diagonal of the cube``from` `math ``import` `sqrt` `# Function to find length``# of diagonal of cube``def` `diagonal_length(a):``    ``L ``=` `0` `    ``# Formula to Find length``    ``# of diagonal of cube``    ``L ``=` `a ``*` `sqrt(``3``)` `    ``return` `L` `# Driver code``a ``=` `5` `# Function call``print``(diagonal_length(a))` `# This code is contributed by Mohit Kumar`

## C#

 `// C# program to find length``// of the diagonal of the cube``using` `System;``class` `GFG``{``// Function to find length``// of diagonal of cube``static` `float` `diagonal_length(``float` `a)``{``    ``float` `L;` `    ``// Formula to Find length``    ``// of diagonal of cube``    ``L = a * (``float``)Math.Sqrt(3);` `    ``return` `L;``}` `// Driver code``public` `static` `void` `Main()``{``    ``float` `a = 5;` `    ``// Function call``    ``Console.Write(diagonal_length(a));``}``}` `// This code is contributed by Nidhi`

## PHP

 ``

## Javascript

 ``
Output:
`8.66025`

Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the Essential Maths for CP Course at a student-friendly price. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

My Personal Notes arrow_drop_up