Function characterized by a relation in the form f(x) = log[latex] _{a}[/latex](x) where a is a strictly positive real number that is different from 1.
Properties
Exponential functions of base a defined by f(x) = [latex]{a}^{x}[/latex] and logarithmic functions of base a defined by f(x) = log[latex] _{a}[/latex](x) are the inverse of one another.
If a > 1, the function defined by f(x) = [latex]{a}^{x}[/latex] is strictly increasing in the set of strictly positive real numbers and if 0 < a < 1, it is strictly decreasing in the set of strictly positive real numbers.
Example
The function
f defined in the set of real numbers by the relation
f(
x) = log[latex] _{2}[/latex](
x) is a logarithmic function with base 2.

A function f defined in the set of real numbers by the relation
f(
x) = log[latex] _{3}[/latex](
x) is a logarithmic function with base 3.