HZAU 1003 Alien invasion

原题
几何题 找公式

#include <cstdio>#include <cstring>#include <cmath>#include <iostream>using namespace std;void solve(){  double d, r;  cin >> d >> r;  double ans = 0;  if (d < r) {    double a = 3 * sqrt(3) * d * d / 4;    double b = M_PI * r * r / 2;    double c = r * r * acos(sqrt(3) * d / (2 * r)) - sqrt(3) * d / 2 * sqrt(r * r - d * d * 3 / 4);    ans = a - b + 3 * c;  }  printf("%.2lf\n", ans);}int main(){//  freopen("input.txt", "r", stdin);  int t;  scanf("%d", &t);  for (int i = 0; i < t; i++) {    solve();  }}