Program to find area of a circle

Area of a circle can simply be evaluated using following formula.

Area = pi * r^{2}where r is radius of circle

## C++

`// C++ program to find area ` `// of circle ` `#include <iostream> ` `const` `double` `pi = 3.14159265358979323846; ` `using` `namespace` `std; ` ` ` `// function to calculate the area of circle ` `float` `findArea(` `float` `r) ` `{ ` ` ` `return` `(pi * r * r); ` `} ` `// driver code ` `int` `main() ` `{ ` ` ` `float` `r, Area; ` ` ` `r = 5; ` ` ` ` ` `// function calling ` ` ` `Area = findArea(r); ` ` ` `// displaying the area ` ` ` `cout << ` `"Area of Circle is :"` `<< Area; ` ` ` `return` `0; ` `} ` |

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## C

`// C program to find area ` `// of circle ` `#include <stdio.h> ` `#include <math.h> ` `#define PI 3.142 ` ` ` `double` `findArea(` `int` `r) ` `{ ` ` ` `return` `PI * ` `pow` `(r, 2); ` `} ` ` ` `int` `main() ` `{ ` ` ` `printf` `(` `"Area is %f"` `, findArea(5)); ` ` ` `return` `0; ` `} ` |

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## Java

`// Java program to find area ` `// of circle ` ` ` `class` `Test ` `{ ` ` ` `static` `final` `double` `PI = Math.PI; ` ` ` ` ` `static` `double` `findArea(` `int` `r) ` ` ` `{ ` ` ` `return` `PI * Math.pow(r, ` `2` `); ` ` ` `} ` ` ` ` ` `// Driver method ` ` ` `public` `static` `void` `main(String[] args) ` ` ` `{ ` ` ` `System.out.println(` `"Area is "` `+ findArea(` `5` `)); ` ` ` `} ` `} ` |

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## Python3

`# Python3 program to find Area of a circle ` ` ` `def` `findArea(r): ` ` ` `PI ` `=` `3.142` ` ` `return` `PI ` `*` `(r` `*` `r); ` ` ` `# Driver method ` `print` `(` `"Area is %.6f"` `%` `findArea(` `5` `)); ` ` ` `# This code is contributed by Chinmoy Lenka ` |

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## C#

`// C# program to find area of circle ` `using` `System; ` ` ` `class` `GFG ` `{ ` ` ` `static` `double` `PI = Math.PI; ` ` ` ` ` `static` `double` `findArea(` `int` `r) ` ` ` `{ ` ` ` `return` `PI * Math.Pow(r, 2); ` ` ` `} ` ` ` ` ` `// Driver method ` ` ` `static` `void` `Main() ` ` ` `{ ` ` ` `Console.Write(` `"Area is "` `+ findArea(5)); ` ` ` `} ` `} ` ` ` `// This code is contributed by Sam007. ` |

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## PHP

`<?php ` `// PHP program to find area ` `// of circle ` ` ` `function` `findArea( ` `$r` `) ` `{ ` ` ` `$PI` `=3.142; ` ` ` `return` `$PI` `* pow(` `$r` `, 2); ` `} ` ` ` `// Driver Code ` `echo` `(` `"Area is "` `); ` `echo` `(findArea(5)); ` `return` `0; ` ` ` `// This code is contributed by vt_m. ` `?> ` |

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**Output:**

Area is 78.550000

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