thanks...

#include <stdio.h>
#include <math.h>

#define PI 3.1416

int main()
{
        double a, r, area;

        scanf("%lf%lf", &a, &r);
        a /= 2;

        if (a >= r) {
                printf("%.3f\n", PI * r * r);
                return 0;
        }
        if (r >= sqrt(2) * a) {
                printf("%.3f\n", 4 * a * a);
                return 0;
        }
        printf("%.3f\n", PI * r * r - 4 * (acos(a / r) * r * r - a *
sqrt(r * r - a * a)));
        return 0;
}

> thanks...
>
> #include <stdio.h>
> #include <math.h> ??????

You can use integral to calculate the area Instead of using any
mathematic function.

I should use ".3lf" instead of ".3f" in the format string
of printf.

> I should use ".3lf" instead of ".3f" in the format string
> of printf.

#define PI 3.1416 // no
#define PI 3.1415926535897932 //yes

Better to use standard M_PI

Edited by author 17.05.2014 17:54