How to prove that when p = (x ^ 2 + y ^ 2) ^ (1 / 2) - > 0, X * y is the infinitesimal of higher order of P?

How to prove that when p = (x ^ 2 + y ^ 2) ^ (1 / 2) - > 0, X * y is the infinitesimal of higher order of P?

Because x ^ 2 + y ^ 2 > = 2|x|y|
p=(x^2+y^2)^(1/2)->0
|x*y|/p