Given an integer **d** which is the length of the diagonal of a pentagon, the task is to find the area of that pentagon.

**Examples:**

Input:d = 5Output:16.4291Input:d = 10Output:65.7164

**Approach:** Pentagon is a regular polygon having five equal sides and all equal angles. The interior angles of pentagon are of 108 degrees each and the sum of all angles of a pentagon is 540 degrees. If **d** is the diagonal of the pentagon then it’s area is given by:

Below is the implementation of the above approach:

## C++

`// C++ program to find the area of` `// Pentagon with given diagonal` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to return the area of the` `// pentagon with diagonal d` `float` `pentagonArea(` `float` `d)` `{` ` ` `float` `area;` ` ` `// Formula to find area` ` ` `area = (d * d * (-5 + ` `sqrt` `(45)) * ` `sqrt` `(` `sqrt` `(20) + 5)) / 8;` ` ` `return` `area;` `}` `// Driver code` `int` `main()` `{` ` ` `float` `d = 5;` ` ` `cout << pentagonArea(d);` ` ` `return` `0;` `}` |

## Java

`// Java program to find the area of` `// Pentagon with given diagonal` `import` `java.text.*;` `class` `GFG{` `// Function to return the area of the` `// pentagon with diagonal d` `static` `double` `pentagonArea(` `double` `d)` `{` ` ` `double` `area;` ` ` `// Formula to find area` ` ` `area = (d * d * (-` `5` `+ Math.sqrt(` `45` `)) * Math.sqrt(Math.sqrt(` `20` `) + ` `5` `)) / ` `8` `;` ` ` `return` `area;` `}` `// Driver code` `public` `static` `void` `main(String[] args)` `{` ` ` `double` `d = ` `5` `;` ` ` `DecimalFormat dec = ` `new` `DecimalFormat(` `"#0.0000"` `);` ` ` `System.out.println(dec.format(pentagonArea(d)));` `}` `}` `// This code is contributed by mits` |

## Python3

`# Python3 program to find the area of` `# Pentagon with given diagonal` `# from math lib import sqrt() method` `from` `math ` `import` `sqrt` `# Function to return the area of the` `# pentagon with diagonal d` `def` `pentagonArea(d) :` ` ` `# Formula to find area` ` ` `area ` `=` `(d ` `*` `d ` `*` `(` `-` `5` `+` `sqrt(` `45` `)) ` `*` `sqrt(sqrt(` `20` `) ` `+` `5` `)) ` `/` `8` ` ` `return` `round` `(area , ` `4` `)` ` ` `# Driver code` `if` `__name__ ` `=` `=` `"__main__"` `:` ` ` `d ` `=` `5` ` ` `print` `(pentagonArea(d))` `# This code is contributed by Ryuga` |

## C#

`// C# program to find the area of` `// Pentagon with given diagonal` `using` `System;` `class` `GFG{` `// Function to return the area of the` `// pentagon with diagonal d` `static` `double` `pentagonArea(` `double` `d)` `{` ` ` `double` `area;` ` ` `// Formula to find area` ` ` `area = (d * d * (-5 + Math.Sqrt(45)) * Math.Sqrt(Math.Sqrt(20) + 5)) / 8;` ` ` `return` `area;` `}` `// Driver code` `public` `static` `void` `Main()` `{` ` ` `double` `d = 5;` ` ` `Console.WriteLine(` `"{0:F4}"` `,pentagonArea(d));` `}` `}` `// This code is contributed by mits` |

## PHP

`<?php` `// PHP program to find the area of` `// Pentagon with given diagonal` `// Function to return the area of the` `// pentagon with diagonal d` ` ` `Function pentagonArea(` `$d` `)` `{` ` ` `$area` `;` ` ` `// Formula to find area` ` ` `$area` `= (` `$d` `* ` `$d` `* (-5 +sqrt(45)) * sqrt(sqrt(20) + 5)) / 8;` ` ` `return` `$area` `;` `}` `// Driver code` `{` ` ` `$d` `= 5;` ` ` `echo` `(pentagonArea(` `$d` `));` ` ` `return` `0;` `}` `//This code is contributed by Mukul singh.` |

## Javascript

`<script>` `// javascript program to find the area of` `// Pentagon with given diagonal` `// Function to return the area of the` `// pentagon with diagonal d` `function` `pentagonArea( d)` `{` ` ` `let area;` ` ` `// Formula to find area` ` ` `area = (d * d * (-5 + Math.sqrt(45)) * Math.sqrt(Math.sqrt(20) + 5)) / 8;` ` ` `return` `area;` `}` `// Driver code` ` ` `let d = 5;` ` ` `document.write(pentagonArea(d).toFixed(4));` ` ` `// This code is contributed by gauravrajput1` `</script>` |

**Output:**

16.4291

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