#入力形式チェック
import math as m
I=input
for t in [0]*int(I()):
	N,X=I().split()
	if len(X)==7:
		assert(X[:2]=="0.")
	else:
		assert(len(X)==8)
		assert(X[:3]=="-0.")
	assert("00000"<=X[-5:]<="99999")
	X=float(X)
	c=m.acos(-X/m.sqrt(X*X+1))
	print(m.sin(int(N)*c+c)/m.sin(c))