A logarithm is the exponent to which a number (called the base) must be raised to obtain a given number. A logarithm finds the exponent
for a base
that results in a specific value
.
Example:
If the base is
and the result is
, what exponent must
be raised to in order to get
? As you can see, the exponent used to reach
from base
is
.
The corresponding logarithmic notation is:

where
is the base,
is the result, and
is the exponent. It's important to note that the base must be positive (
) and not equal to one.
From this definition, we can conclude the following:
- A logarithm with a negative base does not exist.

- The logarithm of a negative number does not exist.

- The logarithm of zero does not exist.

- The logarithm of 1 is zero.

- The logarithm of a base
to itself is 1.

- The logarithm of a power of
is equal to the exponent.

Logarithmic Properties
1Log of a product is the sum of the logs of the factors:

Example:

2Log of a quotient is the log of the numerator minus the log of the denominator:

Example:

3Log of a power is the exponent multiplied by the log of the base:

Example:

4Log of a root is the log of the radicand divided by the index:

Example:

5Change of base formula:

Example:

Since their invention, logarithms have become a powerful tool for handling very large numbers. Because they work with exponents, they transform complex multiplication into simple addition. Thanks to these properties, logarithms make many mathematical operations easier — making them well worth studying.
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