Find Perimeter of a Circle. Take the value of the radius from user.

#include<stdio.h>
#define pi 3.14

void main()
{
    int r;
    float p;
    printf("Enter the value of radius: ");
    scanf("%d", &r); 
    p=2*pi*r;
    printf("Perimeter=%f",p);
}

   

Output
Enter the value of radius: 9
Perimeter=56.520000

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Use Macro to define the value of PI and Find the Perimeter of a Circle

#include<stdio.h>
#define pi 3.14
void main()
{
    int r;
    r=7;
    printf("Perimeter=%f",2*pi*r);
}

   

Output
Perimeter=43.960000

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Find Area and Circumference of a Circle

#include<stdio.h>
#define PI 3.142 

void main() 
{
 float r,a,c;
 printf("\nEnter the radius of circle:\t");
 scanf("%f",&r);
 a=PI*r*r; 
 printf("\nThe area of the circle:\t%f",a);
 c=2*PI*r; 
 printf("\nThe circumference of the circle: %f",c);
}

  

Output
Enter the radius of circle: 2
The area of the circle: 12.568000
The circumference of the circle: 12.568000
Enter the radius of circle: 1
The area of the circle: 3.142000
The circumference of the circle: 6.284000

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