New Year Table

New Year Table

Think:
这是一到数学问题，不过，我觉得这也是考验人品的一道题（精度问题，否则WA ）给出第六组数据 6 9 3 输出YES 。
友情提示： TT (pai) = acos(-1.0);

#include <bits/stdc++.h>#include <math.h>using namespace std;int main(){   int R, r, n;    double pi=3.1415926535897932384626433832795028841971;   cin>>n>>R>>r;   if(r>R)   cout<<"NO"<<endl;   else if(r>(R-r))   {      if(n==1)      cout<<"YES"<<endl;      else      cout<<"NO"<<endl;   }   else   {   if(n==1)   {     if(R>=r)     cout<<"YES"<<endl;     else     cout<<"NO"<<endl;   }   else if(n==2)   {     if(R>=2*r)      cout<<"YES"<<endl;     else     cout<<"NO"<<endl;   }   else   {   double m;   m = (r*1.0)/sin(pi*1.0/n)+r;   if(R-m>=-1e-9)   cout<<"YES"<<endl;   else   cout<<"NO"<<endl;   }   }    return 0;}