What is the product of infinitesimal and infinitesimal? Such as the title

Not necessarily, when x tends to be positive infinity,
(1) Y1 = x squared, y2 = 1 / x, the result is infinite
(2) Y1 = x, y2 = 1 / x, the result is constant
(3) Y1 = radical x, y2 = 1 / x, the result is infinitesimal
It depends

What is "Infinity has no such property as infinitesimal"?
I'm a freshman I really don't know what level these are

The definition of infinitesimal: the variable whose limit is zero is called infinitesimal
(1) Infinitesimal is a variable and cannot be confused with very small numbers;
(2) Zero is the only number that can be infinitesimal
The definition of Infinity: the variable whose absolute value increases infinitely is called infinity
(1) Infinity is a variable and cannot be confused with large numbers;
(2) Infinity is a special unbounded variable, but unbounded variable may not be infinite
(3) The algebraic sum (product) of infinitesimals may not be infinitesimal;
Theorem in the same process, the reciprocal of infinity is infinitesimal; the reciprocal of infinitesimal which is not zero is infinity
one
-= Lim X - > 0 (x > 0) in Y, then y - > is positive infinity at this time
x
same
one
-In = - y, Lim X - > 0 (x > 0), then y - > negative infinity
x

On the thesis of infinitesimal and infinitesimal
I want to combine

Give me some ideas and write my own paper
Infinitesimal, you can search the second mathematical crisis and write down the story
Infinity is more, you can write Cantor set theory, countable sets, bijective and so on
In combination, the reciprocal of infinitesimal is infinity )

What is the product of infinitesimal and infinitesimal? Such as the title