//package misc.ukiepc2025

import kotlin.math.tan

private fun area(m: Int, t: Int, n: Int): Double {
	if (n < 3 || t <= n * m) return 0.0
	val alpha = Math.PI * 2 / n
	val a = t.toDouble() / n - m
	val h = a / (2 * tan(alpha / 2))
	val areaOfTriangle = a * h / 2
	return areaOfTriangle * n
}

private fun solve(magic: Int = 10000) {
	val (m, t) = readInts()
	println((0..minOf(t / m, magic)).maxOf { n -> area(m, t, n) })
}

fun main() = repeat(readInt()) { solve() }

private fun readInt() = readln().toInt()
private fun readStrings() = readln().split(" ")
private fun readInts() = readStrings().map { it.toInt() }