Property 1

The product of an infinitesimal sequence and a bounded sequence is an infinitesimal sequence.

Explanation: The absolute values of the terms of a bounded sequence are restricted by a finite positive number M, that is,

for each natural n.

If is an infinitesimal variable then

.


Property 2
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The sum of two infinitesimal sequences is an infinitesimal sequence

Explanation: If and are infinitesimal sequences then

.


Property 2 Corollary
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The sum of any finite number of infinitesimal sequences is an infinitesimal sequence

Explanation: An idea of a proof is shown in the drawing below, namely, the sum of two infinitesimals is an infinitesimal, the sum of which and a third infinitesimal is also infinitesimal, etc.


Property 3
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The sequence inverse of an infinitesimal sequence is infinite large;
and vice versa:
The sequence inverse of an infinite large sequence is infinitesimal.

Explanation: To verify these propositions, divide number one by 1000, 1000000, 1000000000, and so on. Then divide number one by 0.001, 0.000001, 0.000000001, and so on.