Derivation of the exponential distribution - that infinitesimal

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Discussion Overview

The discussion revolves around the derivation of the exponential function, specifically focusing on the role and implications of the term o(Δt) in the context of this derivation. Participants explore the mathematical foundations and approximations involved, including Taylor expansions and their relevance to the exponential function.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about the purpose and function of the term o(Δt) in the derivation of the exponential function.
  • Another participant explains that o(Δt) encompasses all small terms that are not significant for the derivation, such as (Δt)², (Δt)³, etc.
  • A question is raised regarding the existence of these small terms, suggesting a possible connection to Taylor expansions.
  • A participant confirms that the discussion involves a Taylor approximation to first order, indicating that higher-order terms are neglected.
  • There is a query about the specific function being approximated, with a suggestion that it relates to e^x.
  • Another participant proposes that the relevant expression should be e^x - e^(x+Δt), although they note that they have not verified the prefactors involved.

Areas of Agreement / Disagreement

The discussion includes multiple viewpoints regarding the role of o(Δt) and the nature of the Taylor expansion, with no consensus reached on the specifics of the derivation or the implications of the terms involved.

Contextual Notes

Participants reference Taylor expansions and small term approximations, but the discussion does not resolve the exact nature of these terms or their derivation in the context of the exponential function.

thomas49th
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Hello,

I've been looking at the derivation of the exponential function, here
http://www.statlect.com/ucdexp1.htm
amongst other places, but I don't get how, why or what the o(delta t) really does. How does it help?

It's really confusing me, and all the literature I've looked at just seems to quickly dance over it

Thanks
 
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##o(\Delta t)## contains all small terms the derivation does not want to (and does not have to) care about. Something like ##(\Delta t)^2##, ##(\Delta t)^3## and so on.

Little-o notation
 
why do those terms exist? was there some kind of taylor expansion?
 
Exactly. It is a taylor approximation to first order (linear in Δt) and higher orders are neglected.
 
what the taylor expansion of? e^x ?
 
Should be ##e^x - e^{x+Δt}## with some prefactors I did not check.
 

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