给定一点Q(x,y),连接OQ,取距离Q为d的两点A,B(丨AB丨=2d),过A,B点分别作垂线交圆O于点E,F。EF长度即为题目所求(证明略) #include <bits/stdc++.h> using namespace std; const double pi=3.141592654; int main() { int N;cin>>N; double r,x,y,d; while(N--) { cin>>r>>x>>y>>d; double l=sqrt(x*x+y*y...