/r/math

Photograph via //r/math

This subreddit is for discussion of mathematics. All posts and comments should be directly related to mathematics, including topics related to the practice, profession and community of mathematics.

Welcome to /r/math.

This subreddit is for discussion of mathematics. All posts and comments should be directly related to mathematics, including topics related to the practice, profession and community of mathematics.

Please read the FAQ before posting.


Rule 1: Stay on-topic

All posts and comments should be directly related to mathematics, including topics related to the practice, profession and community of mathematics.

In particular, any political discussion on /r/math should be directly related to mathematics - all threads and comments should be about concrete events and how they affect mathematics. Please avoid derailing such discussions into general political discussion, and report any comments that do so.

Rule 2: Questions should spark discussion

Questions on /r/math should spark discussion. For example, if you think your question can be answered quickly, you should instead post it in the Quick Questions thread.

Requests for calculation or estimation of real-world problems and values are best suited for the Quick Questions thread, /r/askmath or /r/theydidthemath.

If you're asking for help learning/understanding something mathematical, post in the Quick Questions thread or /r/learnmath. This includes reference requests - also see our list of free online resources and recommended books.

Rule 3: No homework problems

Homework problems, practice problems, and similar questions should be directed to /r/learnmath, /r/homeworkhelp or /r/cheatatmathhomework. Do not ask or answer this type of question in /r/math. If you ask for help cheating, you will be banned.

Rule 4: No career or education related questions

If you are asking for advice on choosing classes or career prospects, please post in the stickied Career & Education Questions thread.

Rule 5: No low-effort image/video posts

Image/Video posts should be on-topic and should promote discussion. Memes and similar content are not permitted.

If you upload an image or video, you must explain why it is relevant by posting a comment providing additional information that prompts discussion.

Rule 6: Be excellent to each other

Do not troll, insult, antagonize, or otherwise harass. This includes not only comments directed at users of /r/math, but at any person or group of people (e.g. racism, sexism, homophobia, hate speech, etc.).

Unnecessarily combative or unkind comments may result in an immediate ban.

This subreddit is actively moderated to maintain the standards outlined above; as such, posts and comments are often removed and redirected to a more appropriate location. See more about our removal policy here.

If you post or comment something breaking the rules, the content may be removed - repeated removal violations may escalate to a ban, but not without some kind of prior warning; see here for our policy on warnings and bans. If you feel you were banned unjustly, or that the circumstances of your ban no longer apply, see our ban appeal process here.

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Recurring Threads and Resources

What Are You Working On? - every Monday

Discussing Living Proof - every Tuesday

Quick Questions - every Wednesday

Career and Education Questions - every Thursday

This Week I Learned - every Friday

A Compilation of Free, Online Math Resources.

Click here to chat with us on IRC!


Using LaTeX

To view LaTeX on reddit, install one of the following:

MathJax userscript (userscripts need Greasemonkey, Tampermonkey or similar)

TeX all the things Chrome extension (configure inline math to use [; ;] delimiters)

TeXtheWorld userscript

[; e^{\pi i} + 1 = 0 ;]

Post the equation above like this:

`[; e^{\pi i}+1=0 ;]`


Using Superscripts and Subscripts

x*_sub_* makes xsub

x*`sup`* and x^(sup) both make xsup

x*_sub_`sup`* makes xsubsup

x*`sup`_sub_* makes xsupsub


Useful Symbols

Basic Math Symbols

≠ ± ∓ ÷ × ∙ – √ ‰ ⊗ ⊕ ⊖ ⊘ ⊙ ≤ ≥ ≦ ≧ ≨ ≩ ≺ ≻ ≼ ≽ ⊏ ⊐ ⊑ ⊒ ² ³ °

Geometry Symbols

∠ ∟ ° ≅ ~ ‖ ⟂ ⫛

Algebra Symbols

≡ ≜ ≈ ∝ ∞ ≪ ≫ ⌊⌋ ⌈⌉ ∘∏ ∐ ∑ ⋀ ⋁ ⋂ ⋃ ⨀ ⨁ ⨂ 𝖕 𝖖 𝖗 ⊲ ⊳

Set Theory Symbols

∅ ∖ ∁ ↦ ↣ ∩ ∪ ⊆ ⊂ ⊄ ⊊ ⊇ ⊃ ⊅ ⊋ ⊖ ∈ ∉ ∋ ∌ ℕ ℤ ℚ ℝ ℂ ℵ ℶ ℷ ℸ 𝓟

Logic Symbols

¬ ∨ ∧ ⊕ → ← ⇒ ⇐ ↔ ⇔ ∀ ∃ ∄ ∴ ∵ ⊤ ⊥ ⊢ ⊨ ⫤ ⊣

Calculus and Analysis Symbols

∫ ∬ ∭ ∮ ∯ ∰ ∇ ∆ δ ∂ ℱ ℒ ℓ

Greek Letters

𝛢𝛼 𝛣𝛽 𝛤𝛾 𝛥𝛿 𝛦𝜀𝜖 𝛧𝜁 𝛨𝜂 𝛩𝜃𝜗 𝛪𝜄 𝛫𝜅 𝛬𝜆 𝛭𝜇 𝛮𝜈 𝛯𝜉 𝛰𝜊 𝛱𝜋 𝛲𝜌 𝛴𝜎 𝛵𝜏 𝛶𝜐 𝛷𝜙𝜑 𝛸𝜒 𝛹𝜓 𝛺𝜔

Other Subreddits

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/r/math

3,434,670 Subscribers

0

money help

Help haha..

ok so basically i can’t figure this out because math isn’t my forte, anyway- say i get paid roughly 200$ bi-weekly, and i need 2,600$ how long would it take me to get 2,600$? this is not a school or homework assignment, im genuinely trying to figure this out.

5 Comments
2024/11/03
06:15 UTC

1

applications of orbit stabilizer theorem in combi

i am learning olympiad math, and my teacher asked me if i wanted to learn some abstract math.

so for the past 1 and 1/2 year ive been learning bits of group theory, ring theory etc.

i was just going through my group theory notes, and i was able to solve simple counting questions using the theorem, but couldn't find any thing online.

i was wondering if other people also use |||techniques for olympiad level questions

4 Comments
2024/11/03
05:40 UTC

3

Resources on Solution Methods of DEs about Irregular Singular Points

I am interested in learning about various analytical (not numerical) solution methods to differential equations (ODEs more so but PDEs perhaps as well) about irregular singular points. Most resources/textbooks do not discuss this topic in much detail or at all. I've found some stuff on Laurent series expansion and asymptotic methods but am not completely satisfied. If you have any recommended textbooks or maybe review articles please let me know, thanks in advance!

0 Comments
2024/11/03
04:16 UTC

10

Question in Knot Theory

Does there exist at least two different knots, different from the unknot and also not mirror images of each other, such that they have the same p-coloring for all prime numbers p? Is this a solved problem or an open problem? What name does it go by? Thank you!

3 Comments
2024/11/03
02:16 UTC

0

Is using money a easier and viable method of teaching significant figures to kids?

We all know we use decimals to represent dollars and cents. So this is my plan for my lesson.

Let's say you have 50 cents. You write it as $0.50 cents. Which means we don't care about the zero dollars, we only see 50 cents. And because we usually say 50 cents, the zero isn't significant. So that gives us 2 sig figs.

What about $501? The zero is important because without it, we couldn't have 501, it would just be 51. So that's 3 sig figs.

What if we have $50.00? This is a little more confusing, but in this case, we have $50 and 0 cents. The zero cents tells us that we have no cents. So that is 4 sig figs.

Is this method more congfusing or coud it work?

8 Comments
2024/11/03
01:18 UTC

58

A personal project im working on

Im calculating what numbers have integers as their natural logs, these arent perfect, but theybare close enough where python spits out perfect integers when calculating their natural logs.

These are the ones i have so far ( will not be updated when i work out more)

In(2.718281828459045) ≈ 1

In(7.38905609893065) ≈ 2

In(20.08553692318767) ≈ 3

In(54.59815003314426) ≈ 4

In(148.4131591025766) ≈ 5

P.S. i dont know what a natural log is i just find calculating these incredibly relaxing

Edit: very very annoyed to know that what im doing in calculating the powers of e, & that ive wasted alot of timeo

23 Comments
2024/11/03
01:02 UTC

12

Which parts of generalised knot theory have applications in other areas of math?

I'm a complete novice to knot theory and the generalised question of embeddings of manifolds up to ambient isotopy. However, I know knot theory touches upon combinatorics, algebra and 3-manifolds. Do some of these (or other) areas also similarly depend on questions related to embeddings up to ambient isotopy?

1 Comment
2024/11/03
00:31 UTC

1

Surfaces Described by Non-Conservative Vector Fields.

Conservative vector fields can be described as the gradient for some potential function describing a surface in 3D space, and each vector at every point describes the highest slope of the tangent plane to the described surface at that point. Continuing with this reasoning, what kind of surface might a non-conservative vector field describe, for example <y,-x>? I imagine it would have some kind of helical structure, but couldn't be a function of two variables. Is there some way to determine the shape of this surface exactly, with some kind of implicit function maybe? apologies for any lack of clarity in how this question is posed, only in calc 3 so far!

0 Comments
2024/11/02
07:11 UTC

1

Surfaces Described by non conservative vector fields

Conservative vector fields can be described as the gradient for some potential function describing a surface in 3D space, and each vector at every point describes the highest slope of the tangent plane to the described surface at that point. Continuing with this reasoning, what kind of surface might a non-conservative vector field describe, for example <y,-x>? I imagine it would have some kind of helical structure, but couldn't be a function of two variables. Is there some way to determine the shape of this surface exactly, with some kind of implicit function maybe? apologies for any lack of clarity in how this question is posed, only in calc 3 so far!

0 Comments
2024/11/02
17:37 UTC

146

I'm not entirely sure if this belongs here but

I realized not that long ago that 2025 will be the first year since 414 that can be expressed in base 45 using only base ten digits. (2025 is 100 and 414 is 99). Sorry if this doesn't belong I'll delete it if not

34 Comments
2024/11/02
19:18 UTC

44

Is it normal to always feel a little lost when doing research?

I've started reading papers and books about a research area I'm thinking of going into for my thesis. Actually I've been reading about this area for the past 1.5 years because I did my masters thesis in it and I find it interesting so I'm not a complete beginner. Despite all this when I read papers or books I always feel like there's some background information that I'm missing and that I only understand some of the bigger picture. Of course it's gotten a lot better than when I first started but that feeling is always there to some extent when reading a new paper. What's made me nervous is other PhD students seem to have such a deep understanding on their area of research that I'm beginning to question if this is normal or if I'm just a little slower than everyone else.

10 Comments
2024/11/02
16:43 UTC

169

Who else transitioned from Overleaf to VSCode for presentations and papers?

I've found that Overleaf can become excruciatingly slow and even crash when a project grows too large, especially if you have:

- Too much content within a single `.tex` file

- Too many files or figures in the project

While Overleaf is good for collaboration, these performance issues have made it challenging to use for larger projects. I’ve started transitioning to VSCode with the TeX extension, which offers a smoother experience. I also push everything to GitHub.

Unfortunately, though, I’m not aware of an autosave feature in VSCode, so if you forget to push your work to GitHub or your computer crashes, you risk losing a lot of progress.

By the way, I feel a BURNING hatred in my heart for dealing with inserting figures in Beamer presentations and I absolutely hate making Tikz figures, but I have a fondness for the Madrid theme because the first math class I ever took used it.

The feature that VSCode extension lacks is not having a side panel showing the sections when viewing the raw tex.

65 Comments
2024/11/02
15:01 UTC

9

Some deceptively simple sequences i remember seeing but i dont remember how it went , can someone help?

I know this would sound weird or not welle explained. but i remember where a teacher showed us a sequence which will be easily predicting (without like the formula or something)... i think it was something like (not sure if it was up to 3 or if that was the sequence)

f1=1

f2=2

f3=3

f4=1231312312 (very high number). And then showed us the formula

It was to prove like implictions can't be written sometimes ... I have some class and i want to give this example as why we need to be very accurate etc..

20 Comments
2024/11/02
14:00 UTC

9

How prestigious is the Fermat Math Olympiad (FMO)?

Question is in the title :)

This is the competition I'm referring to: https://globalolympiadsacademy.com/fmo/

4 Comments
2024/11/02
11:28 UTC

8

Curious about a numerical pattern similar to perfect powers

Are there any numbers that follow this pattern:- a^b + b^c + c^d = d^n (where n can be anything)

The logic behind this is choosing one number, raising it to the power of another number, and now the power becomes the base (the power becomes the second number). Repeat this 3 times (find the sum of 3 different such exponentiated numbers) and the sum should be the power of the last number raised to the power of n (where n can be an arbitrary real number). I haven’t had done any computation regarding this so far, but has there been any research paper / mathematical theory regarding such a relationship?

Thank you, and have an awesome day!

11 Comments
2024/11/02
11:25 UTC

1

Question on Polynomial Supremum Bound — Possibly Related to Approximation Theory?

Hey guys:

https://preview.redd.it/vpzzmua3ggyd1.jpg?width=914&format=pjpg&auto=webp&s=68010d8af97764b6df6f6b0be9a40b296da9bb1b

I feel like this question might relate to approximation theory, but I’m not very familiar with the topic. Any insights would be appreciated!

0 Comments
2024/11/02
09:12 UTC

24

Solvable PDEs

I'm studying basic PDE techniques like separation of variables, Fourier series and Fourier transform. The examples they always give are the classics: Laplace's equation, the heat equation and the wave equation. Does anyone know any different PDEs (not necessarily corresponding to any particular physical phenomenon) that can be solved by these methods? If you play around with creating new PDEs you realize why they always stick to the classics - other easy examples are hard to come by. Any suggestions?

11 Comments
2024/11/02
08:38 UTC

52

The sum of 1/n diverges; the sum of 1/p_n diverges. Does the sum of 1/p_{p_n} diverge?

A basic calculus result is that \sum 1/n diverges.

A result of Euler has that \sum 1/p_n diverges where p_i is the i-th prime.

Does this generalize? Does \sum 1/p_{p_n} diverge too?

The first 100 terms of this sum are:

1/3,1/5,1/11,1/17,1/31,1/41,1/59,1/67,1/83,1/109,1/127,1/157,1/179,1/191,1/211,1/241,1/277,1/283,1/331,1/353,1/367,1/401,1/431,1/461,1/509,1/547,1/563,1/587,1/599,1/617,1/709,1/739,1/773,1/797,1/859,1/877,1/919,1/967,1/991,1/1031,1/1063,1/1087,1/1153,1/1171,1/1201,1/1217,1/1297,1/1409,1/1433,1/1447,1/1471,1/1499,1/1523,1/1597,1/1621,1/1669,1/1723,1/1741,1/1787,1/1823,1/1847,1/1913,1/2027,1/2063,1/2081,1/2099,1/2221,1/2269,1/2341,1/2351,1/2381,1/2417,1/2477,1/2549,1/2609,1/2647,1/2683,1/2719,1/2749,1/2803,1/2897,1/2909,1/3001,1/3019,1/3067,1/3109,1/3169,1/3229,1/3259,1/3299,1/3319,1/3407,1/3469,1/3517,1/3559,1/3593,1/3637,1/3733,1/3761,1/3911, ...

That seems too slow to converge. But maybe not.

What about \sum 1/p_{p_{p_n} ?

The first 100 terms are:

1/5,1/11,1/31,1/59,1/127,1/179,1/277,1/331,1/431,1/599,1/709,1/919,1/1063,1/1153,1/1297,1/1523,1/1787,1/1847,1/2221,1/2381,1/2477,1/2749,1/3001,1/3259,1/3637,1/3943,1/4091,1/4273,1/4397,1/4549,1/5381,1/5623,1/5869,1/6113,1/6661,1/6823,1/7193,1/7607,1/7841,1/8221,1/8527,1/8719,1/9319,1/9461,1/9739,1/9859,1/10631,1/11743,1/11953,1/12097,1/12301,1/12547,1/12763,1/13469,1/13709,1/14177,1/14723,1/14867,1/15299,1/15641,1/15823,1/16519,1/17627,1/17987,1/18149,1/18311,1/19577,1/20063,1/20773,1/20899,1/21179,1/21529,1/22093,1/22811,1/23431,1/23801,1/24107,1/24509,1/24859,1/25423,1/26371,1/26489,1/27457,1/27689,1/28109,1/28573,1/29153,1/29803,1/30133,1/30557,1/30781,1/31667,1/32341,1/32797,1/33203,1/33569,1/33967,1/35023,1/35311,1/36887

Is there a finite k where \sum 1/p^{(k)}_n converges?

12 Comments
2024/11/02
00:14 UTC

1

Math+magics! (Like mathematics!)

Count from one as this begins a counting sequence! 0 divided by 0 equals 1infinity! Mathematics generates Love Magic! You cannot start a count with 0. You can count multiple times as much as you need! Credit: Lucifer of the Satanic Temple, Eazy-G, and Moses.

0 Comments
2024/11/02
03:02 UTC

183

I have a ridiculous question that I can't get out of my head until I get an answer

For starters, I'm gonna need this ELI5...

If you zoom out far enough on an exponential curve, would it turn into a right angle? This is, of course providing the line thickness remains constant in the field of view (ie. 1 pixel).

I have no reason for needing an answer other than I can't figure out how to word this in a search engine to achieve an answer and it's been in my head for a whole day.

44 Comments
2024/11/02
01:17 UTC

152

Is liebniz’s derivative notation a fraction or not?

My calc 1 teacher told us that dy/dx isn’t a fraction but in calc 2 when we do U subs we end up treating du/dx as a fraction, when we multiply dx on both sides to substitute for the remaining x in the integral or something

So which one is it? Why do we treat it like a fraction despite it being a technically symbol?

56 Comments
2024/11/01
19:35 UTC

4

Do squigonometric angle identities exist?

I'm specifically looking for an analogue to cos(2x)=2cos^(2)(x)-1 in the p-norm of p=3.

Every proof of the cosine double angle formula that I could find uses either (1) triangle-angle geometry or (2) Euler's identity, and I haven't found a suitable parallel for the squine-3 and cosquine-3.

I need either (1) a squigonometric analogue to Euler's identity or (2) a method to derive the angle identities from either (i) the IVP {x'=-y, y'=x, x(0)=1, y(0)=0} or (ii) the parametrized equation x^(2)+y^(2)=1.

2 Comments
2024/10/31
22:34 UTC

1

Need Advice: Should I Keep Building My “Web of Mathematics and Physics” Project After Finding TGView?

I’ve been working on a project to build an interactive web of mathematics and physics—a kind of hierarchical map that shows how different concepts and theories connect. I’ve been documenting chains of inclusions between mathematical objects to highlight relationships and potential “gaps” in knowledge, hoping it could be useful for students, educators, and researchers.

Here’s the thing: I’ve become completely obsessed with this project. I can’t stop working on it, and I even lose sleep because my mind keeps drifting back to it. It’s pulled me away from my usual work in writing, and I’m constantly thinking about these connections and jotting them down.

But now, after discovering TGView, which already does something similar with visualizing mathematical relationships, I’m wondering if my project brings enough unique value to keep going. Maybe my focus on mapping “gaps” and inclusion chains could make it different enough, but I’m honestly not sure. I’m starting to think that maybe I should step back and go back to my writing.

Any advice or perspectives would be so appreciated—especially if you’ve been in a similar situation.

0 Comments
2024/10/31
21:05 UTC

13

This Week I Learned: November 01, 2024

This recurring thread is meant for users to share cool recently discovered facts, observations, proofs or concepts which that might not warrant their own threads. Please be encouraging and share as many details as possible as we would like this to be a good place for people to learn!

13 Comments
2024/11/01
16:00 UTC

1

Closed formula for series involving factorials?

Hi everyone, I’m trying to find a closed formula for

sum[k=0,∞] x^k!

where |x|<1. WolframAlpha gives exact values for inputs, e.g

x=1/2 leads to sum=1.26563

x=1/3 leads to sum=0.77915

x=1/4 leads to sum=0.562744

x=1/10 leads to sum=0.210001

and so on. I tried different techniques of manipulating the expression, for example writing it as an integral with bounds 0 and x but never got anywhere.

1 Comment
2024/11/01
14:21 UTC

23

Set Theory Multiverse vs Mathematical Truth - Philosophical Discussion

I've been thinking about the set theory multiverse and its philosophical implications, particularly regarding mathematical truth. While I understand the pragmatic benefits of the multiverse view, I'm struggling with its philosophical implications.

The multiverse view suggests that statements like the Continuum Hypothesis aren't absolutely true or false, but rather true in some set-theoretic universes and false in others. We have:

  • Gödel's Constructible Universe (L) where CH is true
  • Forcing extensions where CH is false
  • Various universes with different large cardinal axioms

However, I find myself appealing to basic logical principles like the law of non-contradiction. Even if we can't currently prove certain axioms, doesn't this just reflect our epistemological limitations rather than implying all axioms are equally "true"?

To make an analogy: physical theories being underdetermined by evidence doesn't mean reality itself is underdetermined. Similarly, our inability to prove CH doesn't necessarily mean it lacks a definite truth value.

Questions I'm wrestling with:

  1. What makes certain axioms "true" beyond mere consistency?
  2. Is there a meaningful distinction between mathematical existence and consistency?
  3. Can we maintain mathematical realism while acknowledging the practical utility of the multiverse approach?
  4. How do we reconcile Platonism with independence results?

I'm leaning towards a view that maintains objective mathematical truth while explaining why we need to work with multiple models pragmatically. But I'm very interested in hearing other perspectives, especially from those who work in set theory or mathematical logic.

80 Comments
2024/11/01
13:22 UTC

0

Do you consider mathematics to be a type of literature?

Mathematics seems to be independent of reality, it has its own storytelling styles, and one usually proves some things in order to prove the follow-ups, which reminds me of having a narrative structure.

19 Comments
2024/11/01
12:05 UTC

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