HDU5120(平面几何)

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<iostream>
using namespace std;
double x1,ya,x2,y2;
double dis;
double s1,s2,s3;
double R,r;
double sov(double R,double r) {
    if(dis>=r+R) return 0.0;
    if(dis==0||dis<=R-r) {
        return acos(-1)*r*r;
    }
    double x=(R*R-r*r+dis*dis)/2.0/dis;
    double y=(r*r-R*R+dis*dis)/2.0/dis;
    double seta1=2*acos(x/R);
    double seta2=2*acos(y/r);
    double ans=seta1*R*R/2.0+seta2*r*r/2.0;
    double h=sqrt(R*R-x*x);
    ans-=dis*h;
    return ans;
}
int main()
{
    int t;
    int kase=0;
    scanf("%d",&t);
    while(t--) {
        scanf("%lf%lf",&r,&R);
        scanf("%lf%lf%lf%lf",&x1,&ya,&x2,&y2);
        dis=sqrt((x1-x2)*(x1-x2)+(ya-y2)*(ya-y2));
        s1=sov(R,R);
        s2=sov(R,r);
        s3=sov(r,r);
        double tot=s1-2*s2+s3;
        printf("Case #%d: ",++kase);
        printf("%.6f\n",tot);
    }
    return 0;
}