On Vector Functions With A Parameter

Quest Journals
Journal of Research in Applied Mathematics
Volume 3 ~ Issue 6 (2017) pp: 32-39
ISSN(Online) : 2394-0743 ISSN (Print): 2394-0735
www.questjournals.org
*Corresponding Author: Henrik Stenlund 32 | Page
Research Paper
On Vector Functions With A Parameter
Henrik Stenlunds
29th June, 2017
Received 03 July , 2017; Accepted 05 July, 2017 © The author(s) 2017. Published with open access
at www.questjournals.org
ABSTRACT: A set of equations for removing and adding of a parameter were found in a scalar type vector
function. By using the Cauchy-Euler differential operator in an exponential form, equations for calculation of
the partial derivative with respect to the parameter were developed. Extensions to multiple vector and higher
rank functions were made.
Keywords: vector functions, infinite series, Cauchy-Euler operator, differentiation of
a parameter
Mathematical Classification: Mathematics Subject Classification 2010: 26B12
I. INTRODUCTION
1.1 General
There are two problems of interest in this paper. Sometimes it matters to add a parameter to a vector
function of scalar type. The vector argument can be in two dimensions or higher. The parameter should be an
independent variable. There seems not to exist an operator for adding a parameter of this kind. Secondly, partial
differentiation of a scalar function is usually either very easy or trivial. However, in two or higher dimensions,
there are no immediate general formulas available and the resulting equation is not obvious. The total derivative
of a three-dimensional function is well known but is of little help.
This supposes the ⃗r to have dependence on the parameter t implicitly. But what about the cases where
a vector function of scalar form with a parameter and no other implied dependence of it, is to be treated?
Textbooks offer no solutions in this matter, see for example [1], [2]. To fill in this gap in the following a set of
formulas for addition and removal of a parameter in a vector function and for differentiation with respect to the
parameter in a number of cases is presented. In the following section the basic relations for adding a parameter
to a vector function is presented. Then this equation is extended to more complex cases. Next is developed the
partial derivative equations of the vector functions for various cases. Finally are presented multiple vector cases
and higher rank vector functions. All formal proofs are left out to keep everything simple and readable.
II. OPERATOR EXPRESSIONS
2.1 The Vector Functions
In the following vector functions of varying rank of the type below
are treated. The cases of having a constant vector offset in the argument with variations is studied as well. The
A() is a scalar function of a vector. Thus the parameter function is a multiplier of the vector argument in the
treatment.
2.2 The Cauchy-Euler Differential Operator Extended
In a recent article [3] it was shown that the Cauchy-Euler differential operator

in exponential form has interesting properties when applied to a general function in one dimension. The
assumption for the function is that it has a Taylor's series at the origin. The exponential differential operator is,
on the other hand, defined as a Taylor' power series. In the following one may use the short notation
instead of the full expression
The latter presentation shows the one essential point which makes the great difference to other plain differential
operators, the unity. That is a conservative term while the derivatives are dynamic terms. A simple proof is
given in [3] of the following equation
is a parameter not containing any dependence on x. This result can be used over the complex plane in two
dimensions
One is able to fully control how to turn on and off the parameter. It means that one can implant a
parameter to a vector function which did not have any previous dependence of it. Of course, one can always

multiply a vector argument by a new parameter to the same effect. However, now it is known what is the
external operator to produce the addition or removal. In the following, this is utilized.
2.3 The Partial Derivative with Respect to the Parameter
The first task is to solve the partial derivative
One can now apply equation (9) to lift up the parameter from the inside
and then perform the differentiation to get
This can be done since the argument of the exponential operator commutes with
itself. Finally the original vector function is restored
This is the central equation. The essential requirement is that no variable in this equation has any t dependence.
2.4 Relation to Taylor's Series
Since
a Taylor's series can be built as follows

2.6 The Log Parameter Case
Continue by varying the built-in parameter, to a logarithm
This result is obtained along similar lines as in the preceding case by using a
new variable
2.7 The Trigonometric Functions of the Parameter
The next application is a sin(t) function and it is processed analogously as
Above
The natural extension of cos(t) function follows the same tracks
2.8 The Case of an Arbitrary Parameter Function
The case of an arbitrary function f(t) can be solved

This result is obtained along similar lines as in the preceding case. Here is a derivative of the inverse
function of the f(t). Thus success of this equation is dependent on its existence and range of validity.
By looking once more to equation (16) it is realized that the independence of the two vectors is the key.
Equation (9) can be applied to lift up the parameter from the inside but now one is working with the vector ⃗a
entirely
Likewise, other similar cases for completeness can be found below.

It is tempting to have an option of getting different parameter functions for both vectors above, like equation
(37).
This is correct since the operators act on different independent vectors and commute. The functions
f(t); g(t) have no role at that point. Thus one has managed to expand the number of options greatly. One is then
able to finish this case as follows
The result is not similar to what perhaps might be expected since now the two functions are different.
On the other hand one can derive the following
These results an be attened back to one dimension, like the following
2.10 Higher Rank Vector Functions
As a natural extension of the methodology above it can be applied to a function in vector form. It is expressed as
Its components in Cartesian coordinates are
Therefore, it is not, in general, a function of a vector but of the coordinates only. One can accept true
vectors as well as vector-like functions which do not behave correctly in rotations. Their transformation
properties are not important in the present treatment. One is able to apply equations (8) and (9)

2.11 Generalization to Multiple Parameters The slightly generalized vector function
is different from the form treated above. Processing as before, the following is obtained
which can be proven in the same manner as the similar equations in earlier chapters. The equations (59), (60) are
generalizations covering earlier basic results. By defining a new vector form Cauchy-Euler operator

The results obtained here can be equally applied to vector functions of any rank.
2.12 Orthogonal Coordinate Systems
The expressions obtained above are valid in other orthogonal coordinate systems, like the spherical
polar coordinates. A vector function can be set up in the following form, working as a direct continuation of the
preceding paragraph.
and one is able to obtain again something very familiar
By defining a new vector form Cauchy-Euler opera
II. DISCUSSION
Basic equations for adding and removing a parameter are presented in a vector function of scalar type,
equation (9). The parameter is a multiplier to the vector argument. For multiple vector arguments, it turns out
that one can affect one of the vectors fed in as a summed argument. Eventually, one can separately affect any
with a different parameter function, equation (44).
A set of formulas are developed for calculation of the partial derivative of a vector function, with
respect to a parameter being a multiplier of the vector argument. It was required that no variables in the function
contain any dependence on the same parameter. Equation (16) is the central formula for creation of new
formulas. A set of cases with some typical parameter functions residing in the vector functions were presented.
Equation (45) is a generalization to partial derivative of a two-vector case. Extensions to multiple vectors and
higher ranks are shown with analogous results. Equations (59) and (60) are the most general expressions in
terms of a generalized exponential Cauchy-Euler operator in three dimensions.
REFERENCES
[1]. Whittaker, E.T., Watson, G.N.: A Course of Modern Analysis, Merchant Books (1915), 2nd Edition
[2]. Spiegel, M.: Vector Analysis, Schaum's (1959), 1st Edition, McGraw-Hill
[3]. Stenlund, H.: On Transforming the Generalized Exponential Series, arXiv:1701.00515v1[math.GM] 27th Dec (2016)

On Vector Functions With A Parameter

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