Biology Reference
In-Depth Information
222
LOGARITHM
For numbers like thousand, million, billion or trillion, they can be
represented as 10
3
, 10
6
, 10
9
and 10
12
. Logarithm with base 10 is then defined
as, for example:
log
10
10
3
= 3 .
In general, we have:
log
10
x
n
= n log
10
x .
The number 10 is arbitrary, and we can have other numbers. However,
there is a number denoted by e and defined as:
(1 + 1/n)
n
.
e =
lim
Logarithm with base e (= 2.71829) is usually denoted by In. Similarly, we
have:
ln x
n
= n ln x .
The usefulness of the number e will become clear when we discuss about
derivatives.
In Hill's plot, ln is used so that the non-linear equation based on the Hill's
model of hemoglobin saturation with oxygen at equilibrium can be
converted into a straight line (see Chapter 2).
