Is there a geometrical derivation of e

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Discussion Overview

The discussion revolves around the possibility of deriving Euler's number e through geometrical arguments. Participants explore whether there are any geometric interpretations or definitions of e, particularly in relation to calculus and geometric figures like hyperbolas and circles.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants note that they have not seen any geometrical derivation of e.
  • One participant suggests defining e as the right boundary of the area under the hyperbola, linking it to calculus.
  • Another participant connects e to the unit circle through complex exponentials, indicating a relationship with geometry.
  • There is a discussion about the geometric nature of π as a comparison, with some arguing that both e and π have geometric significance despite not being constructible with compass and ruler.
  • Participants discuss the role of integrals in generating numbers and the differences between areas related to circles and hyperbolas.
  • One participant shares a link to geometric identities involving e, acknowledging that e is less apparent in geometric contexts compared to π.
  • There is a debate about whether the identities involving e are fundamentally tied to the logarithmic function and whether any base could be used in these contexts.
  • Some participants express that the original question may not have been well formulated, leading to confusion about the nature of e's geometric representation.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on whether a geometrical derivation of e exists. Some argue against the possibility, while others suggest that there are connections, albeit not straightforward or universally accepted.

Contextual Notes

Participants highlight limitations in the discussion, including the dependence on definitions and the ambiguity in the question regarding geometric representations of e.

DaTario
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Hi All,

Mr. James Grime from Numberphile channel has said () that the Euler´s number e has basically nothing to do with geometry.
I would like to know if there is any derivation of e based on geometrical arguments.

Best Regards,

DaTario
 
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None that I've ever seen...
 
Thank you, Mark44.
 
DaTario said:
I would like to know if there is any derivation of e based on geometrical arguments.
Probably not what you're looking for, as it is no construction method (as there can't be any with compass and ruler). But you can define ##e## to be the right boundary of the area under the standard hyperbola with its left boundary ##1## that equals ##1##.
$$ 1 = \int_1^e \frac{1}{x}dx$$
 
Yes, fresh_42,

This kind of geometrical association seems to be more inclined to the calculus itself.
Like e is the value of a base ## b ## such that ##b^{i \theta}## corresponds to the complete unit circle as ## \theta ## goes from ## 0 ## to ## 2\pi ##.
 
How would you answer your question if it was ##\pi##? This is clearly a geometric number, but cannot be constructed either. It's the relation between diameter and circumference of a circle or the area of a circle to its squared radius. Circles and hyperbolas are closely related, so I find the definition above quite similar.
 
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Radius, length, areas (total area), curvature are kind of anatomic parts of geometrical objects. Taking a function and doing a definite integral from a to b is a method which can generate almost anynumber, don´t you agree?
 
Take all squares having integer sides, take the inverse of these areas and sum. Finally multiply by 6 and voi la ##\pi ^2##.
 
Besides, the position of the hyperbola in relation to the cartesian system plays an important role.

But the axis in this case are the assimptote...
 
  • #10
DaTario said:
Radius, length, areas (total area), curvature are kind of anatomic parts of geometrical objects. Taking a function and doing a definite integral from a to b is a method which can generate almost anynumber, don´t you agree?
No, I don't. The integral was simply shorter to write than to make a picture of the area. You can also generate any number as the area of a circle which is also an integral.
upload_2017-1-13_5-57-46.png
 
  • #11
fresh_42 said:
No, I don't. The integral was simply shorter to write than to make a picture of the area. You can also generate any number as the area of a circle which is also an integral.View attachment 111493
In the case of circle one can speak of total area. Regarding the hyperbola, it doesn´t happen. I see some difference, but I agree that there is some geometry involved here.
 
  • #12
What is your opinion with respect to the example of the squares above?
 
  • #13
DaTario said:
What is your opinion with respect to the example of the squares above?
What does this have to do with e? Wasn't that what you first asked about?
 
  • #14
Sorry Mark44.
 
  • #15
The importance of my question was in determining what is a geometrically based defnition. The use of ##\pi## was an exercise,
 
  • #16
DaTario said:
The importance of my question was in determining what is a geometrically based defnition. The use of ##\pi## was an exercise,
Here you can find some more "natural" geometric identities involving ##e##
https://en.wikipedia.org/wiki/Logarithmic_spiral

I admit, ##e## is kind of hidden in comparison to ##\pi## and I wouldn't call it a geometric definition as you required. But at least it's not completely out of business.
 
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  • #17
fresh_42 said:
Here you can find some more "natural" geometric identities involving ##e##
https://en.wikipedia.org/wiki/Logarithmic_spiral

I admit, ##e## is kind of hidden in comparison to ##\pi## and I wouldn't call it a geometric definition as you required. But at least it's not completely out of business.
Ok, but the identities on this web page seem to be related to the logarithm as an operation which does not select, in principle, a preferred base.
 
  • #18
DaTario said:
Ok, but the identities on this web page seem to be related to the logarithm as an operation which does not select, in principle, a preferred base.
The first definition they give, for a logarithmic curve, is ##r = ae^{b\theta}##. The next equation they give is for ##\theta##, in terms of the natural log function, ##\ln##. The parametric equations are given in terms of exponential functions involving e.
 
  • #19
ok, but the parameter b tells us that any base could in principle be adopted, isn´t it?
 
  • #20
DaTario said:
ok, but the parameter b tells us that any base could in principle be adopted, isn´t it?
The parameter doesn't have anything to do with it, as far as I can see. You can change an exponential expression in one base to any other base.

$$e^x = b^{x\log_b(e)}, b > 0, b \ne 1$$
However, in the wiki article that fresh_42 linked to, the base was e.
 
  • #21
Mark44 said:
The parameter doesn't have anything to do with it, as far as I can see. You can change an exponential expression in one base to any other base.

$$e^x = b^{x\log_b(e)}, b > 0, b \ne 1$$
However, in the wiki article that fresh_42 linked to, the base was e.

Dear Mark, we are speaking of e appearing as a singular real number in a geometrical context. Statements where e can be exchanged by any other positive real number does not seem to help.
We may say that it was only a matter of the author´s preference.
 
  • #22
DaTario said:
Dear Mark, we are speaking of e appearing as a singular real number in a geometrical context. Statements where e can be exchanged by any other positive real number does not seem to help.
We may say that it was only a matter of the author´s preference.
The number e is the nearly universally preferred base in mathematics topics.

The original question was whether there is any geometric presentation of the natural number e. The answer appears to be, no.

Can we end this thread?
 
  • #23
Mark44 said:
The answer appears to be, no.

The answer is yes, but the OP is not very happy with this answer, it appears.
 
  • #24
I am satisfied with the contributions. It is perhaps the case that the question per se is not so well formulated. I am sorry. You may end the thread. I also believe the answer to the OP is yes.
 

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