Derivative Process Using Fractal Indices k Equals One-Half, One-Third, and One-Fourth ()
1. Introduction
Fractal is a general term used to express both the geometry and the procedures which display self-similarity, scale invariance, and fractional dimension [1] . Geometry deals with shapes or objects described in integral dimension. A point has 0-dimension, a line having 1-dimension, a surface has 2-dimension and the solid has 3-dimensions [2] . However, there are phenomena that are suitably characterized their dimension between any two integral dimensions. A straight line has dimension of 1 and a zigzag has dimension
. Here, the dimension is indicated as fractional dimension―a dimension whose value lies between integral values. Similarly, derivative process is an integral index in nature, such as first, second, third and up to nth derivative. The function obtained from derivative process is very useful in the field of physical science and technology. Thus, it is interesting to describe and analyze the function between integral indices of derivatives. Specifically, the study aimed to explore derivative process using fractal indices k that equals one-half, one-third, and one-fourth.
2. The Derivative Process
The derivative of
with respect to
is itself a function of
, and may in turn be differentiated [3] . The derivative of the first derivative is called second
derivative and is written
or
; the derivative of the second called third derivative,
or
, and so on…
Let
, then the derivatives are as follows::
first derivative
second derivative
third derivative
fourth derivative
fifth derivative
…
…
Repeating the process up to k times, we have
kth derivative (1)
3. Derivatives Using Fractal Indices
Let us consider the function between 0 and first derivative or between first and second derivative. The index fraction indicates that the derivative process is called fractal. These can be denoted as follows:
or
one-half derivative (between zero derivative and first derivative)
or
three-halves derivative (between first derivative and second derivative)
and so on……….
Let
be the function, then
For kth derivative, where k is an element of
, using Equation (1).
(2)
Factorial is equivalent to gamma function [4] as
(3)
Thus, in gamma function
(4)
For negative integer power,
the derivative are as follows:
Let
be the function, then
first derivative
second derivative
third derivative
fourth derivative
fifth derivative
...
...
Repeating the process to k times, we have
kth derivative
or
kth derivative
In factorial form:
(5)
It is equivalent to gamma function as:
(6)
Thus,
(7)
4. Gamma Function
Definition 1. [4] [5] Gamma function is defined as
, for
, then,
(8)
For
Let
we can express in terms of other variable.
Thus,
Getting the product of the two above equations, we have
let
and
Thus,
The gamma function of fraction with multiple of one-half will be obtained as follows:
and
Since the solution of gamma function using integral is complex, the Burnside’s approximate solution [6] [7] ,
,
can be used.
Table 1 shows the actual values of gamma function and the approximate Burnside’s solution. The absolute percentage of error was computed, which it is ranges between 0.06 to 1.5 percent, so Burnside’s equation found acceptable.
Using Burnside’s formula,
Table 1. Comparison of values of gamma function of R+.
then,
or we have
for
then,
5. Roots of Negative 1
The roots of −1 such as square roots, cube roots, fourth-roots, etc. can be obtained using the roots of complex numbers.
Definition 2. [8] Let
, then
, sine
is a multiple of
, then the general form is
, where
.
Definition 3. [8] Let
be the nth root of complex number
then
for
.
The principal root is the root at k = 0, hence the principal nth-root is
Let
Taking the square-root, we have
where k = 0 and 1.
Thus, the roots are:
and
and the principal root is
.
Taking the cube-roots, we have
, where
Thus the roots are
and the principal root is
Taking the fourth-roots, we have
where
Thus the roots are
and the principal root is
.
6. Main Result
For
,
let the function
suppose
then
are the first and second half-derivative.
half-derivative
Differentiate again the function, we have
Thus, getting half-derivative twice is equivalent to first derivative
Let the function
suppose
then
are the first and second half-derivative.
Differentiate again the function, we have
This completes the proof that twice of half derivative is equivalent to first derivative.
For
let
suppose
then
, are the first, second, and third
derivatives respectively.
Thus, triple of one-third derivative is equal to first derivative.
Let
suppose
, then
are the first, second, and third ⅓ derivative respectively.
This completes the proof that the triple of one-third derivative is equal to first derivative
For
Let
suppose
then
are the first, second, third and fourth
derivatives respectively.
This completes the proof that four times of one-fourth derivative is equivalent to first derivative.
Let
suppose
then
are the first, second, third and fourth
derivatives respectively.
This completes the proof that getting the one-fourth derivatives four times is equivalent to one whole or first derivative.
7. Conclusion
The study explored and analyzed the function between integral indices of derivative based on the theoretical deduction of the gamma function. The above solutions and proofs confirmed that derivatives using fractal indices exist everywhere. Derivatives contributed significantly to the field of physical science. It is very interesting to describe and analyze the behavior of functions obtained through derivative process using fractal indices. Likewise, the process being used in this paper can be extended to analyze derivatives of different transcendental functions.