poj1799

简单题

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
    //freopen("D:\\t.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    for (int i = 0; i < t; i++)
    {
        double r;
        int n;
        scanf("%lf%d", &r, &n);
        printf("Scenario #%d:\n%.3f\n\n", i + 1, (1 - 1 / (1 + sin(3.1415926 / n))) * r);
    }
    return 0;
}