Of course, in the
classical calculus the linear functions are the functions having a
constant derivative. However, in the geometric calculus, the exponential
functions are the functions having a constant derivative. And in the
bigeometric calculus, the power functions are the functions having a
constant derivative. (The geometric derivative and the bigeometric
derivative are closely related to the well-known logarithmic derivative
and elasticity, respectively.)
Non-Newtonian calculus has application in science, engineering, and mathematics. Specific fields of application include: fractal geometry, image analysis (e.g., in bio-medicine), growth/decay processes (e. g., in economic growth, bacterial growth, and radioactive decay), finance (e.g., rates of return), the theory of elasticity in economics, marketing, the economics of climate change, atmospheric temperature, wave theory in physics, quantum physics and gauge theory, signal processing, information technology, pathogen counts in treated water, actuarial science, tumor therapy and cancer-chemotherapy in medicine, materials science/engineering, demographics, differential equations (including a multiplicative Lorenz system and Runge-Kutta methods), calculus of variations, finite-difference methods, averages of functions, means of two positive numbers, weighted calculus, meta-calculus, approximation theory, least-squares methods, multivariable calculus, complex analysis, functional analysis, probability theory, utility theory, Bayesian analysis, stochastics, decision making, dynamical systems, chaos theory, and dimensional spaces. For more information, please see the Applications and Citations sections of this website.
NOTE. The six books on non-Newtonian calculus and related matters
by Jane Grossman, Michael Grossman, and Robert Katz are indicated below,
and are available at some academic libraries, public libraries, and
booksellers such as Amazon.com. On the Internet, each of the books can
be read and/or downloaded (free of charge) at HathiTrust and at the Digital Public Library of America.
Michael Grossman. The First Nonlinear System of Differential and Integral Calculus, ISBN 0977117006, 1979. (The geometric calculus) 
Jane Grossman, Michael Grossman, Robert Katz. The First Systems of Weighted Differential and Integral Calculus, ISBN 0977117014, 1980. 
Jane Grossman. Meta-Calculus: Differential and Integral, ISBN 0977117022, 1981. 
Michael Grossman. Bigeometric Calculus: A System with a Scale-Free Derivative, ISBN 0977117030, 1983. 
Jane Grossman, Michael Grossman, and Robert Katz. Averages: A New Approach, ISBN 0977117049, 1983. 
A Quotation from Gauss
The following Carl Friedrich Gauss quotation is from Gauss, Werke, Bd. 8, page 298; and from Memorabilia Mathematica (or The Philomath's Quotation Book) (1914) by Robert Edouard Moritz, quotation #1215.
"In general the position as regards all such new calculi is this - That one cannot accomplish by them anything that could not be accomplished without them. However, the advantage is, that, provided such a calculus corresponds to the inmost nature of frequent needs, anyone who masters it thoroughly is able - without the unconscious inspiration of genius which no one can command - to solve the respective problems, indeed to solve them mechanically in complicated cases in which, without such aid, even genius becomes powerless. Such is the case with the invention of general algebra, with the differential calculus, and in a more limited region with Lagrange's calculus of variations, with my calculus of congruences, and with Mobius' calculus. Such conceptions unite, as it were, into an organic whole countless problems which otherwise would remain isolated and require for their separate solution more or less application of inventive genius."
Three Reviews of the Book Non-Newtonian Calculus
The following review was written by David Pearce MacAdam, and appeared in the Journal of the Optical Society of America (Volume 63, January of 1973), a publication of The Optical Society, which is a member of the American Institute of Physics.
"This [Non-Newtonian Calculus] is an exciting little book, for two reasons: first, its content, and second, its presentation. The content consists primarily of a brief nonaxiomatic description of the fundamentals of various calculi ...The following excerpt is from a review written by Ivor Grattan-Guinness that appeared in Middlesex Math Notes (Volume 3, pages 47 - 50, 1977), a publication of Middlesex University in London, England.
"For each calculus, a gradient, a derivative, and an average are defined; a basic theorem (essentially a mean-value theorem) is stated; an integral is defined; and a fundamental theorem of integral calculus is stated. In Chapter 1, the authors review the essentials of Newtonian calculus and establish the format of presentation that they follow in the later chapters on the various non-Newtonian calculi. Classical problems studied by such men as Galileo and Newton provide examples of, and motivation for, the authors' work. The authors' reference to these problems serves to emphasize the relevance of their results to the concerns of modern science. The greatest value of these non-Newtonian calculi may prove to be their ability to yield simpler physical laws than the Newtonian calculus. Throughout, this book exhibits a clarity of vision characteristic of important mathematical creations.
"The authors have written this book for engineers and scientists, as well as for mathematicians. They have made a dramatic break with tradition and omitted all proofs and many of the mathematical details that place so much of contemporary mathematics writing out of the reach of scientists and engineers. Instead, they have included details that help develop an intuitive conception of their calculi and relate their calculi to well-knows classical problems. The authors apparently feel that their results are of sufficient importance to scientists and engineers to justify these departures from the more traditional style of writing in mathematics. The writing is clear, concise, and very readable. No more than a working knowledge of [classical] calculus is assumed. Mathematicians who feel that their results are of importance to scientists and engineers, but who find little interest among those workers for their results, might consider presenting their work as Grossman and Katz have done. This would do much to reopen channels of communication between mathematicians and scientists and do much to advance both disciplines."
"There is enough here [in Non-Newtonian Calculus] to indicate that non-Newtonian calculi ... have considerable potential as alternative approaches to traditional problems. This very original piece of mathematics will surely expose a number of missed opportunities in the history of the subject."
The following excerpt is from a review written by H. Gollmann that appeared in Internationale Mathematische Nachrichten (Number 105, 1972), a publication of Österreichische Mathematische Gesellschaft in Vienna, Austria.
"The possibilities opened up by the [non-Newtonian] calculi seem to be immense."
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