POJ 题目1905 Expanding Rods（二分，数学几何）

Description

When a thin rod of length L is heated n degrees, it expands to a new length L‘=(1+n*C)*L, where C is the coefficient of heat expansion. 
When a thin rod is mounted on two solid walls and then heated, it expands and takes the shape of a circular segment, the original rod being the chord of the segment. 

Your task is to compute the distance by which the center of the rod is displaced. 

Input

Output

Sample Input

1000 100 0.0001
15000 10 0.00006
10 0 0.001
-1 -1 -1

Sample Output

61.329
225.020
0.000

Source

Waterloo local 2004.06.12

http://blog.csdn.net/lyy289065406/article/details/6648562

ac代码

#include<stdio.h>
#include<math.h>
const double eps=1e-5;
int main()
{
	double l,n,c,s;
	while(scanf("%lf%lf%lf",&l,&n,&c)!=EOF)
	{
		if(l<0&&n<0&&c<0)
			break;
		double low=0,high=0.5*l,mid;
		s=(1+n*c)*l;
		while(high-low>eps)
		{
			mid=(high+low)/2;
			double r=(4*mid*mid+l*l)/(8*mid);
			if(2*r*asin(l/(2*r))<s)
				low=mid;
			else
				high=mid;
		}
		printf("%.3lf\n",mid);
	}
}

POJ 题目1905 Expanding Rods（二分，数学几何）

原文：http://blog.csdn.net/yu_ch_sh/article/details/45696819