/* June 2, 1998 */
/* Program to find the area of circle and circumference */

#include 

#define PI 3.14159

/* function prototype */
double find_area (double r);
double find_circum(double r);

main ()
{
	/* declaration */
	double radius, area;

	/* get radius */
	printf("Enter value of radius> ");
	scanf("%lf", &radius);

	/* find area and circumference */
	/* function call */
	area = find_area(radius);
	printf("The area of the circle is %7.2f\n",area);
	printf("The value of the circumference is %2f \n", find_circum(radius));
}

/* function definitions */

double find_area(double r)
{
	/* declaration */
	double area1;
	
	/* calculation */
	area1 = PI * r * r;

	/* return value */
	return (area1);
}

double find_circum(double r)
{
	return (2.0 * PI * r);
}

    Source: geocities.com/yosemite/rapids/9568

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