UVA 10991 Region

三个圆的圆心连成三角形面积 - 三个扇形面积即可

 

我用asin算出来不对，现在想了想应该是角度问题，如果大于90度的话，用asin是不行的，用acos可以。

 

#include <queue> #include <stack> #include <math.h> #include <stdio.h> #include <stdlib.h> #include <iostream> #include <limits.h> #include <string.h> #include <string> #include <algorithm> using namespace std; const double pi = acos(-1.0); double area_triangle(double a,double b,double c) { double p = (a+b+c)/2.0; return sqrt(p*(p-a)*(p-b)*(p-c)); } double area_fan(double r,double a,double b,double c) { double angle = acos((a*a + b*b - c*c)/(2*a*b)); return r*r*angle/2; } int main() { int ncases; double r1,r2,r3,a,b,c; scanf("%d",&ncases); while( ncases-- ) { scanf("%lf%lf%lf",&r1,&r2,&r3); a = r1 + r2; b = r1 + r3; c = r2 + r3; double area = area_triangle(a,b,c); double fan = ( area_fan(r1,a,b,c) + area_fan(r2,a,c,b) + area_fan(r3,b,c,a) ); printf("%.6lf/n",area - fan); } return 0; }