Expanding Rods

http://poj.org/problem?id=1

 1 #include<cstdio>

 2 #include<cstring>

 3 #include<cmath>

 4 #include<algorithm>

 5 using namespace std;

 6 

 7 const double eps=1e-8;

 8 double n,c,l;

 9 

10 int main()

11 {

12     while(scanf("%lf%lf%lf",&l,&n,&c)&&l!=-1&&n!=-1&&c!=-1){

13         double s=(1+n*c)*l;

14         double low=0,high=0.5*l,mid;

15         while(high-low>eps)

16         {

17             mid=(high+low)/2;

18             double r=(4*mid*mid+l*l)/(8*mid);

19             double ss=2*r*asin(l/(2*r));

20             if(ss<s)

21                 low=mid;

22             else

23                 high=mid;

24         }

25         printf("%.3lf\n",mid);

26     }

27     return 0;

28 }

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