ABSTRACT
What we discuss below is not a new notion but a notation which turns out to be useful in many calculations. We start with a particular definition. Denote by the symbol o(x) (little o of x) any function o(x) = e(x)x, where the function
e(x)! 0 as x! 0. In other words, o(x)! 0 faster than x. Another way to define o(x) is to say that
o(x) x
! 0 as x! 0;
which is the same. For example, x2 = o(x), and x3=2 = o(x), while
p x is not o(x).
