T = int(input())

for _ in range(T):
    n, x = input().split()
    n = int(n)
    x = float(x)

    res = ((x - 1j)**(-n-1) - (x + 1j)**(-n-1)) * (-1)**n / 2j
    res *= (x**2 + 1)**(n/2 + 1)
    print(res.real)