C program to read the radius of a circle and calculate the area and circumference

Source Code:

/*to find the area and circumference of a circle*/

#include<stdio.h>

#include<math.h>

int main()

{

float r, a, c;

printf("Enter the value of radius: ");

scanf("%f", &r);

a = M_PI * r * r;

c = 2 * M_PI * r;

printf("Area of circle = %f", a);

printf("\nCircumference of the circle = %f", c);

return 0;

}

Sample run:

Enter the value of radius: 5

Area of circle = 78.539818

Circumference of the circle = 31.415926