Program to find Circumference of a Circle

Given radius of a circle, write a program to find its circumference.
Examples : 
 

Input : 2
Output : Circumference = 12.566

Input : 8
Output : Circumference = 50.264

In a circle, points lie in the boundary of a circle are at same distance from its center. This distance is called radius. Circumference of a circle can simply be evaluated using following formula. 
 

Circumference = 2*pi*r
where r is the radius of circle 
and value of pi = 3.1415.

// CPP program to find circumference of circle
#include<bits/stdc++.h>
using namespace std;

#define PI 3.1415

double circumference(double r)
{
    double cir = 2*PI*r;
    return cir;
}

// driver function
int main()
{
  double r = 5;
  cout << "Circumference = " 
       << circumference(r);
  return 0;
} 

// Java program to find circumference of circle
import java.io.*;

class Geometry {
    
    // utility function
    static double circumference(double r){

        double PI = 3.1415;
        double cir = 2*PI*r;
        return cir;
    }
    
    // driver function
    public static void main (String[] args) {

        double r = 5;
        double result = Math.round(circumference(r) * 1000) / 1000.0;
        System.out.println("Circumference = "+ result);
    }
}

// This article is contributed by Chinmoy Lenka

# Python3 code to find 
# circumference of circle

PI = 3.1415

# utility function
def circumference(r):
    return (2 * PI * r)


# driver function
print ('%.3f' % circumference(5))

# This code is contributed by Saloni Gupta

// C# program to find circumference of circle
using System;

class GFG {
    
    // utility function
    static double circumference(double r){

        double PI = 3.1415;
        double cir = 2*PI*r;
        return cir;
    }
    
    // driver function
    public static void Main () {

        double r = 5;
        double result =
              Math.Round(circumference(r)
                        * 1000) / 1000.0;
                        
        Console.WriteLine("Circumference = "
                                  + result);
    }
}

// 

<?php
// PHP program to find 
// circumference of circle

$PI= 3.1415;

function circumference($r)
{
    global $PI;
    $cir = 2 * $PI * $r;
    return $cir;
}

// Driver Code
$r = 5;
echo "Circumference = ",
circumference($r);

// This code is contributed aj_36
?>

<script>

// Javascript program to find circumference of circle 

function circumference(r) 
{ 
    let cir = 2*3.1415*r; 
    return cir; 
} 

// driver function 
 
let r = 5; 
document.write("Circumference = "
    + circumference(r)); 

//This code is contributed by Manoj

</script>

Output : 

Circumference = 31.415

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

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

This article is contributed by Saloni Gupta .