import java.io.*;
import java.util.*;

public class pahom_mb {
    public static void main(String[] args) throws IOException {
        try (Input in = new Input()) {
            int c = in.nextInt();
            for (int nc = 0; nc < c; ++nc) {
                int m = in.nextInt();
                int t = in.nextInt();
                int maxN = t / m;
                double best = 0;
                for (int n = 3; n <= maxN; ++n) {
                    double side = t / 2.0 / n - m / 2.0;
                    double area = n * side * side / Math.tan(Math.PI / n);
                    if (area >= best) {
                        best = area;
                    } else {
                        break;
                    }
                }
                System.out.println(best);
            }
        }
    }

    private static class Input implements Closeable {
        private final BufferedReader in;
        private StringTokenizer st;

        Input() throws IOException {
            in = new BufferedReader(new InputStreamReader(System.in));
            st = new StringTokenizer(in.readLine());
        }

        int nextInt() throws IOException {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(in.readLine());
            }
            return Integer.parseInt(st.nextToken());
        }

        public void close() throws IOException {
            in.close();
        }
    }
}