2258.cpp

这是哈尔滨工业大学acmOJ的源代码

/*  This Code is Submitted by wywcgs for Problem 2258 on 2006-05-29 at 10:26:02 */ 
#include <cstdio>
#include <cmath>

const int VN = 1024;

int main()
{
	double total[VN] = { 0 };
	int n, m, i, t, T;
	
	scanf("%d", &T);
	for(t = 0; t < T; t++) {
		scanf("%d %d", &n, &m);
		int c = m / n; m %= n;
		double alpha = 2*M_PI/n;
		for(i = 1; i < n; i++) {
			double r = sqrt(2-2*cos(alpha*i));
			total[i] = total[i-1] + r*alpha;
		}
		printf("%.2lf\n", total[n-1]*c+total[m]);
	}
	
	return 0;
}