How to calculate the shaded area in a diagram with c programming?

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

const double pi = 3.1416;

double r1, r2, diff;

printf("Enter r1: ");

scanf("%lf",&r1);

printf("Enter r2: ");

scanf("%lf",&r2);

diff = pi * (r1*r1 - r2*r2);

printf("Radii of bigger shaded area is and smaller circles are %f and %f cm . The shaded area is %f sq cm\n", r1, r2, diff);

return 0;

}

I'm giving you the solution since this is an absolute no-brainer, even without the diagram:

float r1 = 4.5;

float r2 = 2.0;

float pi = 3.1416;

float area = r1*r1*pi - r2*r2*pi;

cout << "Radii of bigger and smaller circle are " << r1 << "cm and " << r2 << "cm. The shaded area is " << area << "cm²";