/*--------------------------------------------------
created by st10 at Wed Mar 10 13:33:34 PST 2010
--------------------------------------------------*/
#include <iostream>
#include <cmath>
#include "circ_area.h"
using namespace std;


/*--------------------------------------------------
 Contract: ring_area : double double -> double
 Purpose: expects the outer radius of a ring and
          the radius of its "hole", and produces
          the area of that ring

 Examples: ring_area(10, 1) == circ_area(10) - circ_area(1)
           ring_area(10, 1) == 311.01741
--------------------------------------------------*/

double ring_area(double outer, double inner)
{
    return circ_area(outer) - circ_area(inner);
}