2.2. Equivalence of infinitesimal

Let be and - infinitely small with .

If a then is infinitely small of a higher order compared to . In this case, it is said that there is " about small" from and write down: .

If a where k is a non-zero number, then and - infinitely small one order . In this case, it is said that there is " Oh big" from and write down: .

In the particular case, if then infinitesimal and called equivalent and write: ~ .

If a then . Consequently, is infinitely small of a higher order compared to ( ).

In calculating the limits, the following infinitesimal equivalence is often used: