View Code of Problem 106

        #include<stdio.h>
        #include<math.h>
        int main()
        {
        	double x1,x2,y1,y2;
        	double r;
        	while(scanf("%lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&r)!=EOF)
        	{
        			double x=x1-x2;
        			double y=y1-y2;
        			double l=sqrt(x*x+y*y);
        		if(l==0)
        		{
        			printf("重合\n");
        		}
        		else if(l>2*r)
        			{
        				printf("相离\n");
        			}
        			else if(l==2*r)
        			{
        				printf("相切\n");
        			}
        			else
        			{
        				double ang1=acos((r*r+l*l-r*r)/(2*l*r));
        				double ang2=acos((r*r+l*l-r*r)/(2*l*r));
        				double area=ang1*r*r*2-sin(ang1)*r*l;
        				printf("相交 %.2lf\n",area);
        			}
        	}
        }