# Largest triangle that can be inscribed in a semicircle

• Last Updated : 16 Mar, 2021

Given a semicircle with radius r, we have to find the largest triangle that can be inscribed in the semicircle, with base lying on the diameter.
Examples:

```Input: r = 5
Output: 25

Input: r = 8
Output: 64```

Approach: From the figure, we can clearly understand the biggest triangle that can be inscribed in the semicircle has height r. Also, we know the base has length 2r. So the triangle is an isosceles triangle.

So, Area A: = (base * height)/2 = (2r * r)/2 = r^2

Below is the implementation of above approach

## C++

 `// C++ Program to find the biggest triangle``// which can be inscribed within the semicircle``#include ``using` `namespace` `std;` `// Function to find the area``// of the triangle``float` `trianglearea(``float` `r)``{` `    ``// the radius cannot be negative``    ``if` `(r < 0)``        ``return` `-1;` `    ``// area of the triangle``     ``return` `r * r;``}` `// Driver code``int` `main()``{``    ``float` `r = 5;``    ``cout << trianglearea(r) << endl;``    ``return` `0;``}`

## Java

 `// Java  Program to find the biggest triangle``// which can be inscribed within the semicircle``import` `java.io.*;` `class` `GFG {``   `  `// Function to find the area``// of the triangle``static` `float` `trianglearea(``float` `r)``{` `    ``// the radius cannot be negative``    ``if` `(r < ``0``)``        ``return` `-``1``;` `    ``// area of the triangle``    ``return` `r * r;``}` `// Driver code`  `    ``public` `static` `void` `main (String[] args) {``        ``float` `r = ``5``;``    ``System.out.println( trianglearea(r));``    ``}``}``// This code is contributed ``// by chandan_jnu.`

## Python 3

 `# Python 3 Program  to find the biggest triangle``# which can be inscribed within the semicircle` `# Function to find the area``# of the triangle``def` `trianglearea(r) :` `    ``# the radius cannot be negative``    ``if` `r < ``0` `:``        ``return` `-``1` `    ``#  area of the triangle``    ``return` `r ``*` `r`  `# Driver Code``if` `__name__ ``=``=` `"__main__"` `:` `    ``r ``=` `5``    ``print``(trianglearea(r))` `# This code is contributed by ANKITRAI1`

## C#

 `// C# Program to find the biggest``// triangle which can be inscribed``// within the semicircle``using` `System;` `class` `GFG``{``    ` `// Function to find the area``// of the triangle``static` `float` `trianglearea(``float` `r)``{` `    ``// the radius cannot be negative``    ``if` `(r < 0)``        ``return` `-1;` `    ``// area of the triangle``    ``return` `r * r;``}` `// Driver code``public` `static` `void` `Main ()``{``    ``float` `r = 5;``    ``Console.Write(trianglearea(r));``}``}` `// This code is contributed``// by ChitraNayal`

## PHP

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## Javascript

 ``
Output:
`25`

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