扇形面积=R*R*Hudu(扇形弧度)/2;

弧长L=R*Hudu(扇形弧度）

 

/*  * zoj1597.c  *  *  Created on: 2011-9-21  *      Author: bjfuwangzhu */ #include
     
       #include
      
        #define pi acos(-1.0) #define eps 1.0e-8 double distance(double x1, double y1, double x2, double y2) {
   return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); } int main() {
   #ifndef ONLINE_JUDGE     freopen("data.in", "r", stdin); #endif double x1, y1, r1, x2, y2, r2, r12, dis, temp, res; while (~scanf("%lf %lf %lf %lf %lf %lf", &x1, &y1, &r1, &x2, &y2, &r2)) {
           dis = distance(x1, y1, x2, y2);         r12 = fabs(r1 - r2); if (dis - r1 - r2 > eps) {
               printf("%.3lf\n", 0.0); continue;         } if (dis - r12 > eps) {
               temp = acos((dis * dis + r1 * r1 - r2 * r2) / (2 * dis * r1)) * 2;             res = r1 * r1 * temp / 2.0 - r1 * r1 * sin(temp) / 2.0;             temp = acos((dis * dis + r2 * r2 - r1 * r1) / (2 * dis * r2)) * 2;             res += r2 * r2 * temp / 2.0 - r2 * r2 * sin(temp) / 2.0;             printf("%.3lf\n", res); continue;         }         temp = r1 > r2 ? r2 : r1;         printf("%.3lf\n", pi * temp * temp);     } return 0; }