Talk:E (mathematical constant)

We need a simpler way to calculate e

I can't figure out most of the math on the page. Can anybody help me? —Preceding unsigned comment added by 66.167.177.92 (talk) 01:59, 6 February 2010 (UTC)

e = (1+1/n)^n where n is infinite, that should probably be included. 64.233.227.21 (talk) 19:33, 23 March 2010 (UTC)

Italics

Is there any reason why e is set in italics? See for example the IUPAC guidance. —DIV (128.250.80.15 (talk) 04:15, 7 April 2008 (UTC))

Yes, I'd say that's why. Are you reading it differently than I am? Dicklyon (talk) 04:27, 7 April 2008 (UTC)

Paragraph 7 says "The symbols π, e (base of natural logarithms), i (square root of minus one), etc. are always roman". It really bothers me to see stuff such as $\displaystyle e^{\frac {eV}{k_{\scriptscriptstyle {\text{B}}}T}}$ where the two es refer to different things. -- Army1987 (t — c) 01:17, 11 October 2008 (UTC)

Yep, looks like he was reading it differently that I was; I missed that detail. Should fix... Dicklyon (talk) 03:53, 11 October 2008 (UTC)

OK, I changed e to roman. We'll see if this get supported, or reverted. Support would mean help converting the ones in math mode. Dicklyon (talk) 04:25, 11 October 2008 (UTC)

Judging by a random selection of mathematics texts I've just looked at, it's fairly widespread practice to put e in italics. Additionally, Wikipedia:Manual of Style (mathematics) has this to say:

"On the other hand, for the differential, imaginary unit, and Euler's number, Wikipedia articles usually use an italic font".

Adding in the fact that we now have two competing styles in the same article, roman and italic (which is the sort of inconsistency style manuals advise against), I'm afraid I'm inclined to revert this. I'm sure there are other guides out there that say this is wrong, but the writers of said guides may not take into account that typing "\mathrm{e}" is not going to be popular with people writing formulae in TeX on a near daily basis.

There's an informative discussion on this issue here in which a number of people argue the pros and cons of italics vs roman type, if anyone's interested. Ash (talk) 16:59, 12 October 2008 (UTC)

Very interesting; looks like Tufte decided on the roman in the end; perhaps because of the standard this guy pointed out: "I have just discovered, through downloading a PDF file which Google pointed out under the URL http://www.tug.org/TUGboat/Articles/tb18-1/tb54becc.pdf that not only is making e=2.71828... roman instead of italic no longer forbidden, it is now compulsory... if one wishes to be compliant with ISO standards and recommendations made by the International Union of Pure and Applied Physics." – Does anyone have access to this ISO standard that's mentioned therein? Is the IUPAP same as IUPAC? Dicklyon (talk) 17:58, 12 October 2008 (UTC)

I can answer the last one: International Union of Pure and Applied Physics (IUPAP) and International Union of Pure and Applied Chemistry (IUPAC) are separate organisations. And I believe this is the ISO standard that's being referred to in the discussion. (Funny, I spent some fruitless minutes trying to search iso.org when I should've just checked Wikipedia.) Ash (talk) 19:12, 12 October 2008 (UTC)

Thanks for finding ISO 31-11#Exponential and logarithmic functions. It links a NIST document that explicitly calls for e and pi to be Roman. Of course, there's still the issue of usual practice that we need to reconcile. Dicklyon (talk) 23:40, 12 October 2008 (UTC)

I'd say that the IUPAC is totally wrong here. First of all, this is a mathematics article, not a chemistry article. So the applicability of this guideline is rather tenuous. Secondly, there is no such standard in mathematical literature. On the contrary, as has been discussed in other contexts here on Wikipedia, the recommendation to use roman fonts for mathematical operators and symbols runs completely against well-established almost universally adopted norms in mathematics. siℓℓy rabbit (talk) 17:20, 12 October 2008 (UTC)

That's not my impression. It's true that italic e is pretty widespread, due to the ease of doing it that way in TeX. But roman e is also widespread, where other variables are italic. So there's at least evidence that many people are willing to go to the trouble of following a standard that explains a good reason to distinguish mathematical constants from variables. Dicklyon (talk) 18:00, 12 October 2008 (UTC)

What about using ℯ ("U+212F SCRIPT SMALL E = error; natural exponent") so that people will see whatever their favourite font uses? (Unicode also has ⅇ ("U+2147 DOUBLE-STRUCK ITALIC SMALL E • sometimes used for the natural exponent"), but I've never seen it used anywhere.) -- Army1987 (t — c) 13:05, 18 October 2008 (UTC)

I think it's just likely to get changed back by someone who doesn't have fonts properly installed, like this recent incident over at Sobolev space illustrates. siℓℓy rabbit (talk) 14:27, 18 October 2008 (UTC)

Proposed change to introductory sentence

I propose to change the intro, which currently reads thus:

The mathematical constant e is the unique real number such that the value of the derivative (slope of the tangent line) of the function f(x) = e^x at the point x = 0 is exactly 1.

to this:

The mathematical constant e is the unique real number such that the function e^x has the same value as its slope, for all values of x.[1]

I think this better conveys a memorable, comprehensible, geometric interpretation of e. Also, as a followon to that sentence, one might add this:

More generally, the only functions which are equal to their own derivatives are of the form Ce^x, where C is a constant.[2]

This is a really important general statement, and the previous sentence leads nicely into it.JCLately (talk) 03:45, 16 April 2008 (UTC)

Your proposed new definition can be shown, with enough work, to follow from the existing simpler definition. I believe that a definition should be as simple as possible (but no simpler). Dicklyon (talk) 05:44, 16 April 2008 (UTC)

The existing "definition" can be shown (with less work, I believe) to be a consequence of my proposed first sentence. So if the two statements are mathematically equivalent, on what basis is one simpler than the other? I didn't present my lead sentence as a definition, although it could be so considered, and that is specifically mentioned in the reference that I provided. No reference has been offered that the previous formulation is widely accepted as the definition of e, but it isn't my intention to get into a semantic argument as to what constitutes the definition of e, either historically or according to some formal criterion.

As it currently reads, the lead sentence, while correct and reasonably concise, is not particularly useful as a general statement, it is not especially memorable, and it fails to convey the very special, non-arbitrary character of e. If a person were to read only one sentence of this article, which one better encapsulates the essence of e? Whether or not my formulation is "simpler", whether or not one regards it as definitive, I think it says far more about what is e, and what is its significance.

The caption on the accompanying graphic is virtually identical to the previous intro sentence, so what's the point of saying the same thing twice? We can keep the graphic and its caption, but I think my proposed change to the intro sentence would be an improvement. JCLately (talk) 01:52, 17 April 2008 (UTC)

The purpose of the figure and its caption is to illustrate the defining characteristic described in the lead sentence. It seems to me that the slope of the tangent line at one point is much simpler and more concise than the general derivative everywhere. Dicklyon (talk) 02:56, 17 April 2008 (UTC)

I agree with Dicklyon. This definition is a more primitive one, requiring only the slope of a tangent line, and should therefore be favored over the definition that requires the notion of the derivative as a function. Futhermore, there is a picture to go along with the current defintion, while it is unclear if a compelling picture can be drawn to illustrate the definition JC has in mind. Finally, let us not forget that this article is on the mathematical constant e, rather than the natural exponential function. silly rabbit (talk) 03:04, 17 April 2008 (UTC)

Whatever may have been the purpose of the figure and its caption, the issue I'm raising pertains to the Wikipedia guideline on article introductions. To wit, "It should establish context, summarize the most important points, explain why the subject is interesting or notable..." and "should be written in a clear, accessible style so as to invite a reading of the full article". I do not see how the present lead sentence is either simpler or more concise than my alternative, but more importantly, the present formulation seems considerably less useful and illuminating. One is required to comprehend the concept of slope (aka derivative) in either case: what is the benefit of a statement about the slope at a particular point, rather than an infinitely more useful statement about the slope at any point on the same curve? I appreciate your having provided a reference to support this rather unusual definition of e, but I think you'd find many more references to the the way that I put it.

In further reply to silly rabbit, it would be simple enough to illustrate the more general theorem/definition with a graph showing a family of curves of the function f(x) = a^x for various choices of a, noting that only for the special value a = e does the slope equal the value at every point on the curve, including at x = 0. As to your observation that this article is about e, not the exponential function, I don't see how this distinguishes between the two alternatives at hand, since both refer to the same function. Furthermore, it would be pretty hard to do justice to the concept of e without prominent mention of the exponential function, as they are intimately and inextricably related! JCLately (talk) 21:34, 17 April 2008 (UTC)

My own preference is to define e as the base of the natural logarithm, as indicated above in the talk page. In fact, this was in my own favored version of the lead many moons ago. However, people who are unfamiliar with the many approaches to the subject of mathematical analysis seemed to feel that this definition was circular. Eventually the present one was settled upon. As you have agreed, a more complicated graph is needed to illustrate the definition of e you are offering here. Furthermore, it is arguably less geometrical, since it invokes a certain global property of the function, namely its derivative at every point, rather than the local (in fact, infinitesimal) property of the slope of its tangent line. silly rabbit (talk) 22:23, 17 April 2008 (UTC)

The definition that I found surprisingly often in searching books was pretty much opposite of that. First they define the natural log (as the integral of 1/x, perhaps?). Then they define its inverse function exp(), and then the define e as exp(1) and then show that exp(x) is equal to e^x.

I still think that the slope of a tangent line at a point is a much "simpler and more concise" concept than the derivative of a function, and don't get why JCLately says it's not. The former is understandable to persons who don't know a bit of calculus; the latter is not. Neither is the definition of ln(x) via integration. I think it pays for wikipedia to have a definition that can be easily understood by "Algebra II" students. Dicklyon (talk) 22:44, 17 April 2008 (UTC)

Sometimes it's hard to determine who is replying to whom. I basically agree with everything you just said, for the record. silly rabbit (talk) 23:22, 17 April 2008 (UTC)

OK, I see a point of confusion that is the result of my having used a piped wikilink to slope in my proposed new first sentence. I meant to use the word slope in the sense that is synonymous to derivative, but perhaps it would be clearer to express it as the slope of the tangent line. My intention in the first sentence is to convey the geometrical meaning in such a way that it should be clear to someone without any understanding of calculus. I don't buy the argument that this more "global" definition is any less geometric than the "local" one, because it tells you something about the shape of the curve e^x, whereas something that describes only the characteristics of a single point on the curve tells you nothing about its shape. So one could reasonably argue that the broader definition is more geometric, and it does not require the comprehension of anything more complex than the slope of a tangent line, exactly the same concept used in the present lead sentence. But again, I think this line of argument misses the point that the lead sentence should, above all, express something notable and significant, which offers an immediate insight into why e is a very special number. As the article says: "The number e is one of the most important numbers in mathematics". The current article lead doesn't really give the reader a clue as to why this should be, and it is not a particularly useful statement, whether you call it a definition or a theorem. On the other hand, what I am proposing is a statement that directly paraphrases an extremely useful general statement about e in terms that can be visualized geometrically without an understanding of calculus.

I'm not sure how you got the idea that I agreed that a more complicated graph is needed to illustrate the definition of e that I am offering. In fact, the same diagram could be used, simply by adjusting the caption to note that besides the specific point (0, 1) at which a tangent is drawn, it is also true that slope = value at every other point on e^x, and not on any of the other curves. JCLately (talk) 02:19, 18 April 2008 (UTC)

Since e is transcendental there will naturally be a challenge presenting it to the novice. Appeal to calculus is probably inappropriate when alternatives are available. My preference is the use of area and a nod to the pioneers St-Vincent and de Sarasa. As mentioned above in "A suggestion from history", the constant arose when one wondered when an area determined by the hyperbola xy = 1 becomes equal to one. Now at "Alternative characterizations" in the article there is the Image: hyperbola E.svg which illustrates alternative #5. A different image at hyperbolic angle could also be used to illustrate for the novice how e is the number where the hyperbolic angle is one. With this approach based on area there would be no immediate need to refer to logarithms (the base of natural log) or to tangents to a curve.Rgdboer (talk) 23:21, 17 April 2008 (UTC)

There was not consensus for the change JCLately has made to the lead sentence. I'm not going to revert, because I don't feel very strongly one way or the other, but I do prefer the old version over this one. silly rabbit (talk) 05:52, 24 April 2008 (UTC)

I actually agree with JCLately's proposed change. Whenever the slope of a tangent line is mentioned, you're already doing calculus. Whether we're using it for a single point or the whole curve, we're asking for the same level of background from the reader. Moreover, that this property holds for the point x=0 is not interesting (in both the mathematician's sense of the words as well as the usual). The fact that e^x always takes the same value as its slope has bountiful applications throughout mathematics, the fact that e^x takes the same value as its slope at x=0 does not. In my opinion, we should try to as general as possible with our statements, except when this will require our reader have unreasonable knowledge. Since both proposed openings require the same knowledge (comprehension of the slope of the tangent line/derivatives), I say we should go with JCLately's. Last Octagon (talk) 17:43, 18 September 2009 (UTC)

If you want to re-open this discussion from over a year ago, I recommend starting a new section at the bottom. I'll disagree, though, since the concept of slope of a function as a function is considerably more complex than the slope of a tangent line as a number. The notion of a "tangent line" is a "pre calculus" idea, even if you need calculus to formalize it, and the slope of a line is an elementary concept in algebra.

"The mathematical constant e is the unique real number such that the value of the derivative (slope of the tangent line) of the function f(x) = e^x at the point x = 0 is exactly 1."

Self-reference in the definition. Why introduce e in terms of the derivative of e^x? I propose to instead use the integral of 1/x from 1 to e. —Preceding unsigned comment added by Jcottem (talk • contribs) 22:02, 8 November 2009 (UTC)

e in computer culture

The article has the text below under the heading above:

In contemporary internet culture, individuals and organizations frequently pay homage to the number e.

i am tempted to change this. the examples which follow are certainly not relevant internet culture, which nowadays is dominated by facebook and youtube videos of hanna montana. these examples are, instead, excellent examples of nerd culture.

please speak up if you have an opinion about my change proposal.

--Philopedia (talk) 08:32, 5 May 2008 (UTC)

zero fright ?

A graph without origin is like icing without a cake. The graph is missing a zero numeral in each axis. Jclerman (talk) 06:02, 19 June 2008 (UTC)

The compound-interest problem

I find it interesting that this example is given using dollars. Which nation's currency would that have been at the time Bernoulli was working on the problem? Huw Powell (talk) 20:30, 6 September 2008 (UTC)

Since Jacob Bernouilli was Swiss, it probably would have been Swiss francs. siℓℓy rabbit (talk) 20:35, 6 September 2008 (UTC)

Correction: It would have most likely been Basel thalers, since the Franc was yet to be introduced. siℓℓy rabbit (talk) 20:41, 6 September 2008 (UTC)

Variant of the compound interest problem

There's a variant of the compound interest problem that may be worth mentioning in the article: How long does it take for compound interest at x percent to double the initial capital? As x tends to zero, the length becomes (e - 2)*100/x. Grutness...wha? 23:32, 13 October 2008 (UTC)

I'm no mathematician

I'm no mathematician but on the part where proving dy/dx of log (base a) x is 1/x, h changes to u.

I dont know how to change this, or I dont know if this is wactually wrong/right but it looks wrong. DarkRef (talk) 18:03, 13 January 2009 (UTC)

Actually, u=h/x is a change of variable. I have hopefully clarified this point. siℓℓy rabbit (talk) 18:20, 13 January 2009 (UTC)

Other complex numbers (excluding i[j] and e)?

• Aren't there other complex numbers except for i or e? It doesn't have to be a vowel or consonant. If not, I myself have a hypothesis for values of other complex numbers. -DtW —Preceding undated comment added 01:43, 1 March 2009 (UTC).

e isn't a complex number (and if I'm to be completely pedantic neither is i). 137.205.74.230 (talk) 23:13, 9 March 2009 (UTC)

One wants u+v to be a complex number whenever u and v are and this requires that every real number, including 1 and e, is also a complex number and every every pure imaginary number, including i , is as well.--Gentlemath (talk) 22:15, 21 March 2009 (UTC)

• Well, it depends on the context. Technically (that is, to be unnecessarily set-theoretically pedantic), 1-the-integer is a different object from 1-the-rational, 1-the-real, 1-the-complex number, and even 1-the-natural-number, although the different objects in certain senses behave similarly (as multiplicative identity in Q, R, and C, for example). But i is always complex, because C is the simplest context in which it appears. Pirate pete (talk) 01:18, 4 July 2009 (UTC)

How to make a complex number

• Take your real number (say, e)
• Multiply it by i (ei)
• Add another real number (say, π + ei)
• Job done.

I hope that answers all questions. ²³¹₉₁Pa (chat me!)

Definition for E given incorrectly !

The stated expression, "the limit as n goes to infinity of (1 + 1/n)^n", evaluates to 1, not E; the definition should be the summation of (1 + 1/n)^n for n = 1..infinity. —Preceding unsigned comment added by 68.63.171.24 (talk • contribs)

No, your definition is wrong. After three terms of the summation, the total is already over 3, and increasing. The expression in the article is correct - try using n={10, 100, 1000} in the equation, which gives e~{2.5937, 2.7048, 2.7169} - as you can see, this is converging to e. Mindmatrix 15:25, 18 May 2009 (UTC)

Sorry! I could have saved myself embarrassment if I had evaluated the expr (1.001)^1000 at wolframalpha.com; though that site evaluates (1.0001)^10000 (and all higher powers) as zero! Why not just say "limits of computation exceeded" or whatever? That site will never replace Google, or rival HAL, though it is a handy shortcut to all kinds of information. —Preceding unsigned comment added by 68.63.171.24 (talk) 15:54, 18 May 2009 (UTC)

These things happen...it's curious that Alpha evaluates that expression to 0, yet gets it right for the expression (1 + 1/10000)^10000. Probably some quirk with the way the Mathematica backend works. Aside: I never realized just how slowly that expression converges to e. Mindmatrix 18:14, 19 May 2009 (UTC)

It also works for numbers in the form of (1 + 1e-n) ^ 1e+n, where n <= 75, such as (1 + 1e-32) ^ 1e+32. If n <= 32, n correct digits (n-1 decimal places) will be displayed without any further adjustments. If 33 <= n <= 64, click "More digits" once; if 65 <= n <= 75, do it twice. This won't work for n > 75, however. The trick is not to use numbers with a decimal point unless they convert to binary or hex precisely. Glenn L (talk) 21:32, 19 May 2009 (UTC)

Well, the "More digits" option is not currently working, but you can still input numbers up to about (1 + 1/3e33) ^ 3e33: [3]. That displays e to 34 significant figures (33 decimal places), all correct. For larger numbers, fewer digits are displayed, with only "3" displayed for x between 4e65 and 1e66 and nothing displayed beyond that. --Glenn L (talk) 23:45, 15 August 2009 (UTC)

Formula

I only know some basic calculus but how can the formula equal 2.71...? In theory it should equal 1 because if you do 1/∞ that equals 0 so if you add 1 that equals one then raise that to the power of ∞ you get 1. I know that I am wrong but if someone could just explan how and why it equals e in plain english then it would be much appreciated. Thank you, 95jb14 (talk) 16:26, 6 July 2009 (UTC).

The reason it works is that you don't evaluate (1 + 1/x) ^ x at x = ∞, but at a suitably large value of x that approaches ∞. For example see the following WolframAlpha algorithm: [4]. As explained above the algorithm doesn't currently work for any larger number, but if you use your computer's Calc program you can substitute larger numbers to show that the expression does indeed converge to e. Glenn L (talk) 18:45, 6 July 2009 (UTC)

I used Calc myself and could get the x as high as 2,000,000,000 - some 47 times larger than the WolframAlpha agorithm - and got a value for e of 2.718 281 827 779... or 2.718 281 828 correct to 9 decimal places. Unfortunately, the algorithm won't correctly work for Calc beyond two billion due to how Calc functions.

I have an Ativa AT-36 Scientific Calculator (from Office Depot) that takes x all the way to 625 billion (625,000,000,000), with a vaule for e of 2.718 281 828 457 7... which is correct to 11 decimal places and is very close to the true value of 2.718 281 828 459 0... for e. Even my calculator failed after this: for x = 640 billion, the last digits of e decreased to "... 457 1..." (they should have increased); for x = 800 billion, the last digits jumped to "... 460 4...", which is too large because (1 + 1/x) ^ x can never exceed the true value of e unless x is less than 0, in which case the expression approaches e from the other direction. Glenn L (talk) 19:31, 6 July 2009 (UTC)

I am sorry, I feel I made a horrifically bad mistake with my calculator at some point in my calculations and just ended up with 1000000 somehow, but now I understand thanks, 95jb14 (talk) 19:38, 6 July 2009 (UTC).

Only Function Equal To Own Derivative?

The intro states: "More generally, the only functions equal to their own derivatives are of the form Ce^x, where C is a constant." I don't know if it's enough to need clarification, but this is only true for x=!0. Also, f(x)=0 is another function equal to its own derivative, which granted is when C=0 in the first case. This is nitpicking, but should it be edited? Baddox (talk) 17:37, 23 July 2009 (UTC)

What do you mean? x is just a dummy variable used to describe the function. It doesn't have any particular value. The mappings $x\mapsto Ce^{x}$ are indeed the only functions that equal their derivatives. No change is necessary. Eric119 (talk) 18:44, 23 July 2009 (UTC)

Algebraic Number

An "algebraic number" is actually the root of a polynomial with rational coefficients not integer coefficients; the corresponding term for integer coefficients is an "algebraic integer". I'm going to go ahead and change integer coefficients to rational coefficients in the article heading. Last Octagon (talk) 17:13, 18 September 2009 (UTC)

Sorry, I forgot that you can multiply through any polynomial with rational coefficients to obtain one with integer coefficients, (although it will no longer be monic), and therefore the statement was correct previously. However, I'll leave it as rational, since it is just as correct and it may avoid similar confusion. Last Octagon (talk) 17:19, 18 September 2009 (UTC)

Global maximum/minimum

More generally, $x=e^{-1/n}$ is where the global maximum occurs for the function

$\!\ f(x)=x^{x^{n}}.$

I've checked this on a graphing utility, and it is a global maximum when n < 0, and a global minimum when n > 0. Clarphimous (talk) 19:12, 13 October 2009 (UTC)

Proposal: e Approximation with Mnemonic

I added an external link to e Approximations (http://mathworld.wolfram.com/eApproximations.html) and recommend adding the following to the article under a new section "approximations of e".

For this particular approximation, it 1) has a mnemonic 2) is suitable for entry on a basic scientific calculator that lacks the constant 3) is high precision (8 significant digits)

e ~~ (pi ^ 4 + pi ^ 5) ^ (1/6)
Source: Castellanos (1988ab)

The mnemonic is "2, 3, 4, 5, 6" with 2 representing e, 3 being pi, 4 and 5 the exponents and 6 the root. Thanks.

Drakcap (talk) 00:30, 16 October 2009 (UTC)

There's no such mnemonic in the source you cite, so let's don't start one here. Dicklyon (talk) 00:44, 16 October 2009 (UTC)

The approximation is cited and there are none in the article. We should include one or more examples -- we have them for pi. Do you have an argument for not including one or more approximations? The source notes that one as curious. I know it's curious. It uses pi and has the numbers 4, 5, 6. It's pretty neat. We don't need to add my comments or why I think it's curious, but it's important to include it and up to two others. We can use the word "curious" because it's used in the source. Does anyone have constructive comments? Drakcap (talk) 11:49, 17 October 2009 (UTC)

This seems a silly e approximation to me as (a) it is semi-difficult to remember and (b) you can't use it for computations unless you already have pi, and (c) since its only accurate to about 8 digits. Remembering 10 digits of accuracy is much simpler, since you probably already know the first few digits (2.718) and then if you just remember that 1828 repeats twice after the first 2.7, you have ten digits of accuracy with 2.7 1828 1828 Jimbobl (talk) 06:03, 7 December 2009 (UTC)

True. Drakcap (talk) 10:10, 19 December 2009 (UTC)

Some Russian mathematicians remember a few places just "2.7" and then the year of the much admired writer Leo Tolstoy's birth repeated twice:2.718281828. I've heard a U.S. mnemonic based on Andrew Jackson's presidency that gives twice as many digits, but I forget what it is. (I never much admired Jackson. Maybe I need a mnemonic for that mnemonic.)--Richard L. Peterson69.181.166.171 (talk) 19:36, 2 March 2010 (UTC)

Removal of infobox

Based upon a discussion at Wikipedia talk:WikiProject Mathematics#"Infoboxes" on number articles, I've removed the infobox from the article. If anyone disagrees, could you please join the discussion there. Thanks, Paul August ☎ 12:34, 18 October 2009 (UTC)

I have suggested centralizing this discussion to Wikipedia_talk:WikiProject_Mathematics#Irrational_numbers_infobox as it refers to an infobox occurring in several articles. Please go there to build consensus on this edit. RobHar (talk) 19:36, 18 October 2009 (UTC)

Title: "mathematical constant" versus "number"

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was no consensus for move.--Fuhghettaboutit (talk) 12:42, 5 November 2009 (UTC)

---

E (mathematical constant) → E (number) — $e$ is just as much of a number and a mathematical constant as 2 is, and surely we should prefer "2 (number)" over "2 (mathematical constant)". Using a clunkier, less direct term to describe $e$ suggests that in some sense, $e$ is less of a number than 2, which is of course preposterous. —Saric (Talk) 20:40, 28 October 2009 (UTC)

I agree that "e (number)" would be a better name than "e (mathematical constant)". Since this is such a well-established article, perhaps the best approach would be a move request. Jim (talk) 21:15, 28 October 2009 (UTC)

Good idea; I've subst'd the template above. —Saric (Talk) 22:01, 28 October 2009 (UTC)

e (number) seems like a much more appropriate choice for distinguishing the number from e. Robo37 (talk) 22:16, 28 October 2009 (UTC)

• Agree the proposed change is definitely a positive change. ~~ GB fan ~~ ^talk 23:08, 28 October 2009 (UTC)
• Oppose "E-numbers" are numbers of the form (3.45E-16) or whatever, frequently in common speech, like High School math students speech. 70.29.209.91 (talk) 03:58, 29 October 2009 (UTC)
• Oppose However, the preceding commenter has E numbers (number codes for food additives and are usually found on food labels throughout the European Union) confused with E notation (which represents times ten raised to the power, thus replacing the x 10ⁿ). I believe that E (constant), which also redirects to E (mathematical constant), would be a still better name than E (number). ---Glenn L (talk) 04:57, 29 October 2009 (UTC)
  • Comment I don't have it confused at all, as I said, when used in speech by a lay person it's an "E-number". 70.29.209.91 (talk) 05:10, 29 October 2009 (UTC)
  • I agree that "e (constant)" is an improvement over "e (mathematical constant)". —Saric (Talk) 10:49, 29 October 2009 (UTC)
• Oppose until someone shows that other similar articles use "number". See Category:Mathematical constants. Johnuniq (talk) 07:05, 29 October 2009 (UTC)

The only items in the category that use parentheses for disambiguation are:

• Degree (angle)
• E (mathematical constant)
• 6174 (number)
• Period (number)

So "number" seems to be the convention, so much as there is one. (Not to mention 0 (number), 1 (number), and so on.) This article's the outlier. —Saric (Talk) 09:53, 29 October 2009 (UTC)

Period (number) doesn't help here, as the article is not about an individual constant but about a property that a number may or may not have. Degree (angle) is even more obviously irrelevant, the article being related to mathematical constants such as π, but not about them. And 6174 (number) merely follows the convention for numbers given as their decimal representation. There is a big difference between the disambiguation requirements of π or e on one hand and 1, 2, 6174 on the other. And e even has some disambiguation problems that π doesn't have, such as E numbers. I believe the main reason why people tend to refer to e as a "number" more often than as a "constant" is the arbitrary but historically common distinction between Euler's number and Euler's constant. Hans Adler 10:37, 29 October 2009 (UTC)

• Oppose. There is nothing wrong with just calling e a number, but there is also nothing wrong with calling it a mathematical constant. It happens to be both. The latter term is much more effective as a disambiguator, as pointed out by others above. Hans Adler 08:04, 29 October 2009 (UTC)
• Oppose for the reasons already mentioned (confusion with E number). A move to E (constant), however, would be an improvement. --ἀνυπόδητος (talk) 14:02, 29 October 2009 (UTC)
• Agree. Number is shorter and clearer and the longer term doesn't do anything to help with disambiguation. I really doubt people will confuse "e (number)" with "E-number" and a hat note could be added to handle the unlikely event that it does.--RDBury (talk) 14:08, 29 October 2009 (UTC)
• Oppose Pi says 'This article is about the mathematical constant'. It doesn't say about the number. Letters used for constants are typically called constants not numbers. A number refers to something that stands on its own like 2.3 or even 1+i Dmcq (talk) 16:45, 29 October 2009 (UTC)
• Agree "e (number)" seems better because it's simpler. Notice that this uses lower case; obviously "E (number)" with a capital E would be wrong. "e (constant)" would also be OK. Michael Hardy (talk) 18:03, 29 October 2009 (UTC)
• Oppose on balance. Lots of numbers might get represented by e in some context. For example, is the electronic charge a "number"? Not in the sense we're thinking about, but the word "number" is vague enough that the point is arguable. Current title is clearer. --Trovatore (talk) 20:35, 29 October 2009 (UTC)
  • Comment I also don't like e (constant). For example the charge on the electron might be called a "constant" even more easily than a "number". I could see a reasonable argument for e (real number), I suppose, though I don't see any real advantage of that over the current title. --Trovatore (talk) 20:50, 29 October 2009 (UTC)
    • I agree that it makes more sense to call the charge of an electron a "constant" than to call it a "number". Most physical quantities are not dimensionless numbers, but rather are what you get when you multiply a number by a physical unit of measurement. The distance from here to Chicago is not a number. I can take a number multiplied by one mile, or a different number multiplied by one kilometer, and it's the same distance. Michael Hardy (talk) 06:14, 30 October 2009 (UTC)
      • Sure, but the point is still that the word number in itself is so poorly defined that it doesn't really exclude many things that might be denoted by e. If you don't like the electronic charge, how about the number of edges in a graph? That's clearly a number.
      • With articles like 2 (number) we don't have this problem — there aren't a lot of things that 2, the number, can really mean (I suppose we could distinguish 2 the natural number from 2 the real number, but it's unlikely we'd want separate articles for them). For e it's quite different.
      • Finally, I have to disagree with Saric when he claims it's absurd to say that 2 is less of a number than e — one sense of the word number is specifically natural number. --Trovatore (talk) 07:26, 30 October 2009 (UTC)
• Oppose: The current title, "e (mathematical constant", had one important advantage over the proposed alternative and other suggestions: it is unambiguous. That, along with recognizability, are the main objectives that article titles should strive for. Plus, no one has identified a genuine problem that renaming the article would solve. Personal preference of some editors for a different title is not a sufficient reason to change the title, in the absence of some objective showing that the change would improve the encyclopedia for its readers. —Finell (Talk) 02:31, 30 October 2009 (UTC)
• Oppose, per above. Oleg Alexandrov (talk) 17:45, 30 October 2009 (UTC)
• Motion to close debate There is clearly not going to be a consensus to rename the article so I don't see how further debate will be productive.--RDBury (talk) 18:32, 30 October 2009 (UTC)
  • Second, consensus will not be achieved, close as no consensus and do not move the article. ~~ GB fan ~~ ^talk 18:37, 30 October 2009 (UTC)
• Questions: Shouldn't we have consistency here? Why are we going to have sets of articles of the form 0 (number) and e (mathematical constant)? And what exactly is a non-mathematical constant? Unless a good reason is given for this inconsistency (I don't consider "it's ambiguous" a good reason since (a) just about every word in the English language is ambiguous in some way; (b) the current page would undoubtedly be the most common usage of e (number); and (c) disambiguation pages and hatnotes are designed to handle to less common usages and are used extensively), I support e (number). Ben (talk) 23:35, 30 October 2009 (UTC)
  • Well, I don't see these cases as really parallel. The symbol 0 is a numeral; its default denotation is actually a number, and only because of a (somewhat questionable IMO) WP convention that has numerals by default denoting years, is there even an issue here. The symbol e on the other hand is all sorts of things; in a sufficiently abstract sense I suppose you can also call it a numeral, but most people wouldn't. It's more like a variable that in certain contexts doesn't vary. --Trovatore (talk) 02:17, 31 October 2009 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

The square root of e

Hi everyone,

      I found this guy who claims that he found a formula for the square root of e:

http://photo.163.com/photo/420111197702177316/#m=2&ai=51057471&pi=2371457280&p=1 The formula itself is interesting, but i can't verify it. and he said that no one in the world could do this before. Can you guys check on it? —Preceding unsigned comment added by 70.36.134.226 (talk) 10:03, 28 November 2009 (UTC)

${\frac {1}{{\sqrt {e}}-1}}=1.5+4\sum _{n=1}^{\infty }{\frac {1}{1+(4n\pi )^{2}}}$

is certainly an interesting formula, reminiscent of the Leibniz formula for pi. With transposition, the above becomes:

${\sqrt {e}}=1+{\frac {1}{1.5+4\sum _{n=1}^{\infty }{\frac {1}{1+(4n\pi )^{2}}}}}$

It starts with 1.65566... for the 1st term and decreases slowly, adding one decimal place of precision for each power of 10 terms computed.

${\sqrt {e}}=[1;1,1,1,5,1,1,9,1,1,13,1,1,17,1,1,...,4k+1,1,1,...]$

is much better, and the following triples this speed (3 extra digits per single iteration):

${\sqrt {e}}=1+{\cfrac {2}{3+{\cfrac {1}{12+{\cfrac {1}{20+{\cfrac {1}{28+{\cfrac {1}{36+\ddots }}}}}}}}}}$

--Glenn L (talk) 01:35, 29 November 2009 (UTC)

I doubt anyone much cares about the speed of convergence — we have lots of efficient ways of computing e to as many places as you like. The more interesting question to me would be, assuming the equation is true, why is it true? I see no obvious reason it should be.

And until I see a "why", or at least a more reliable reference, I'm going to have to remain skeptical on whether it is true. Ramanujan proposed lots of formulas that looked like this (or, often, even much more Baroque), without explanation. A lot of them were in fact correct. But some of them were wrong. --Trovatore (talk) 02:09, 6 February 2010 (UTC)

Thanks. So is this some kind of new discovery that is worth talking about or is really nothing but something easily derived based on existing formulas?

—Preceding unsigned comment added by 70.36.134.226 (talk) 10:03, 28 November 2009 (UTC) 

Picture caption makes no sense

The caption to the second illustration (a graph of y = 1/x with part of the area under the curve in color) reads as follows:

"The area under the graph y = 1/x is equal to 1 over the interval 1 ≤ x ≤ e."

This is unintentionally ambiguous, and it is easier to read the unintended interpretation (which makes no sense) than the intended one. An improvement would be:

"The area between the x-axis and the graph y = 1/x, for the range 1 ≤ x ≤ e, is equal to 1 ."

70.231.243.83 (talk) 21:05, 12 March 2010 (UTC)

Significance of e^(1/e) and the function (e^(1/e))^x

Hi guys, I recently discovered this interesting fact, do you think it should be included onto this page? If ∑A_i=x, then max(∏A_i)=(e`)^x where e`=e^(1/e). The proof is quiet easy so I will omit it. —Preceding unsigned comment added by 70.36.134.226 (talk) 09:31, 16 March 2010 (UTC)

I'm not sure what's happening in the maximum on the left-hand side of that equation, because there's only a single term, the product. Also, are the A_i intended to be constant? If so, how is it that you can combine them in such a way that they equal a function of x? Ozob (talk) 10:56, 16 March 2010 (UTC)

It seems to me from the description that the OP is trying to maximize $\prod _{i=1}^{n}A_{i}$ over the set $\{\langle A_{1},\dots ,A_{n}\rangle \in [0,+\infty )^{n}\mid \sum _{i=1}^{n}A_{i}=x\}$. However, then the correct result is $(x/n)^{n}$. In any case it's self-admitted WP:OR.—Emil J. 11:10, 16 March 2010 (UTC)

Yes this is what I meant, except that in this case n is also a variable. I am sorry for not making myself clear the first time. Here is a detailed explanation. (I am not familiar with wikipedia's formula editor so my I kindly direct you to this pdf file. thanks.)

http://the-genius-group-from-uc-berkeley.googlegroups.com/web/e'.pdf?gsc=NGWgoQsAAAC8VQb16TVXxaJMlrgnpls1

(ignore the "genius" part from the link, we just just joking.) —Preceding unsigned comment added by 99.57.188.93 (talk) 00:20, 17 March 2010 (UTC)

It's still wrong. The problem only makes sense for natural numbers n, you cannot plug in n = x/e. The actual maximum will be smaller unless x is an integer multiple of e. In any case, it's unsourced original research, and a fairly trivial at that. (Let alone the fact that the derivation you present is far from a complete proof.)—Emil J. 11:21, 17 March 2010 (UTC)

So it's a notational issue. So how about, if na=x, then max (a^n=e'^x), now it makes sense right? Anyway if you guys don't care about it that's fine, I just thought if maybe interesting to mention the number e^(1/e). If I really cared I would go on and try to formulate a strict proof and publish it on some other website that so you guys will not consider it "original research". But why waste that time? It's just math anyway.

This problem actually arise from another problem where you are asked to cut a positive integer into several smaller integers to maximize their product. For example, for 10, you can cut it into five 2s, whose product is 2^5=32, or two 2s and two 3s, whose product is 4*9=36. Eventually it turns out that the more 3s and 2s you use the larger the final product will be. In choosing between 3s and 2s 3 is preferred. And a further discussion shows that the reason why 3 and 2 are preferred is because they are closer to e. And because 3 is closer to e it is preferred over 2. When the integer restriction is relaxed, the maximum becomes e'^x, where x is the number you are trying to divide. I have a very long and tedious proof of these but since you guys don't look so interested I won't waste your time. Peace out. —Preceding unsigned comment added by 70.36.134.226 (talk) 13:12, 17 March 2010 (UTC)