Function with Euler's constant

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Discussion Overview

The discussion revolves around alternative representations of the function frac{x}{e^{x}-1}, specifically seeking a trigonometric form without using Bernoulli numbers. Participants explore various mathematical approaches and concepts related to this function.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about expressing frac{x}{e^{x}-1} as a trigonometric function without involving Bernoulli numbers.
  • Another participant questions the meaning of "display as a trigonometric function" and suggests using the identity e^x = cos(x) + i sin(x), but later states this approach is not valid.
  • A different participant proposes substituting x with ix as a potential method.
  • One participant discusses the Taylor series expansion of e^{x}-1 and its relation to frac{e^{x}-1}{x}, presenting it as a series.
  • Another idea involves using a triangle to relate f(x)=x and a local linearization of e^x -1, suggesting the use of Taylor series for arcsin or arccos.
  • A participant expresses interest in understanding the role of Bernoulli numbers in the series expansion leading to frac{x}{e^{x}-1} and references Faulhaber formulas.
  • Another participant notes the occurrence of Bernoulli numbers only at even indices, except for B#1, and provides a link to the Riemann zeta function for further context.

Areas of Agreement / Disagreement

Participants present multiple competing views and approaches without reaching a consensus on a specific trigonometric representation or the role of Bernoulli numbers.

Contextual Notes

Some participants express uncertainty regarding the validity of certain mathematical identities and the implications of using trigonometric forms. The discussion includes references to series expansions and specific mathematical concepts that may require further exploration.

eaglechief
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Hello all,

is there an alternative way of displaying

##\frac{x}{e^{x}-1}##

as a trigonometric function, not using the bernoulli-numbers ?

Thanks in advance
 
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I'm not sure what you mean by "display as a trigonometric function". Would writing [itex]e^x[/itex] as [itex]cos(x)+ i sin(x)[/itex] help?
 
HallsofIvy said:
I'm not sure what you mean by "display as a trigonometric function". Would writing [itex]e^x[/itex] as [itex]cos(x)+ i sin(x)[/itex] help?
Regardless of what it means, writing it this way would not help since it is not true. It is ##e^x##, not ##e^{ix}## ...
 
Well, you can replace x by ix.
 
Turn it upside down: [itex]e^{x}-1=\frac{x}{1!}+\frac{x^{2}}{2!}+...[/itex], so [itex]\frac{e^{x}-1}{x}=\frac{1}{1!}+\frac{x}{2!}+\frac{x^{2}}{3!}...[/itex]. Don't know if that helps.
 
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Maybe set up a triangle with one side ## f(x)=x ## and the other side a local linearization of ## e^x -1 ##, then use Taylor series for arcsin or arc cos? Just an idea, Ihave not worked it out.
 
Thanks for your answers, I do think the answers of Svein and WWGD do help me the best.

Basically, i am trying to understand, what the Bernoulli Numbers "do" and why they can be developed in a series expansion leading to the simple result x/(e^x-1).
I started by checking that Faulhaber-formulas, where the bernoulli-numbers appear in the last term while summarising x^2n with escalating x. Second, i wonder why they "appear" only with 2n index (except B#1).

thx for any hint !
 

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