poj 1905 Expanding Rods 二分

 /**
 题解晚上写
 **/
 #include <iostream>
 #include <math.h>
 #include <algorithm>
 #include <cstdio>
 using namespace std;
 const double esp = 1e-;
 int main()
 {
     double l,n,c;
     while(cin>>l>>n>>c){
         if(l<&&n<&&c<)
             break;
         double ll;
         ll = (+n*c)*l;
         double low,high;
         low =;
         high= l/;
         double r,mid;
         while(high-low>esp){
             mid = (high+low)/2.0;
             r = ((mid*mid*)+(l*l))/(*mid);
             if(*r*asin(l/(*r))<ll)
                 low = mid;
             else
                 high = mid;
         }
         printf("%.3lf\n",high);
     }
     return ;
 }