this post was submitted on 27 Apr 2025
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Funny

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[–] grrgyle@slrpnk.net 78 points 2 months ago (9 children)

Shit like this makes me realise why people become mathematicians. You just play around with numbers and find funny facts about them.

[–] driving_crooner@lemmy.eco.br 51 points 2 months ago* (last edited 2 months ago) (1 children)

So, years ago in college in Linear Algebra our professor said to us to study about idempotent matrices. So I checked out that wiki page and saw the example for 2x2 matrix, that are composed by the numbers 3, -6, 1 and -2. And I was like wait a second, 3×-2=-6 there's no way they are not relationship there, so I started trying other numbers, and found and proved (using induction) that any n, -n(n-1), 1, -(n-1) is an idempotent matrix. At the test there were no questions about that, and I was short of 0.5 poits to pass the class without having to present a final exam and I told my professor that I spent a lot of time learning that and that even discovered something and proved he pass me the chart and asked me to proved it, after that he gave the missing points. Was really good.

[–] Kusimulkku@lemm.ee 5 points 2 months ago (1 children)

You need to put the name inside the brackets and the link inside the parentheses.

idempotent matrices

[–] GraniteM@lemmy.world 16 points 2 months ago (1 children)

I myself once learned 380 digits of π, when I was a crazy high-school kid. My never-attained ambition was to reach the spot, 762 digits out in the decimal expansion, where it goes "999999", so that I could recite it out loud, come to those six 9s, and then impishly say, "and so on!"

—Douglas Hofstadter

[–] grrgyle@slrpnk.net 5 points 2 months ago (1 children)

That would be an amazing party trick.

[–] grrgyle@slrpnk.net 5 points 2 months ago (5 children)

Actually come to think of it, even more amazing in the age of smart phones, when it's possible to easily verify to numbers you're reciting.

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[–] mnemonicmonkeys@sh.itjust.works 8 points 2 months ago

Then you try to figure out why they do be like that

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[–] match@pawb.social 46 points 2 months ago (5 children)

gonna need this in every base

I'll start with base 2:

1/1 = 1

[–] mattd@programming.dev 16 points 2 months ago

Base 3:

21 / 12 = 1.1012101210121012

[–] MelodiousFunk@slrpnk.net 10 points 2 months ago (1 children)

gonna need this in every base

...all of them?

[–] match@pawb.social 3 points 2 months ago

for great justice

[–] LeninOnAPrayer@lemm.ee 8 points 2 months ago

I'm gonna need a formal proof for this.

[–] PattyMcB@lemmy.world 6 points 2 months ago

We should be friends

[–] NosferatuZodd@lemmy.world 3 points 2 months ago (1 children)
[–] itslilith@lemmy.blahaj.zone 6 points 2 months ago (1 children)
[–] NosferatuZodd@lemmy.world 3 points 2 months ago

Who are You, Who are so Wise in the Ways of Science?

[–] rainrain@sh.itjust.works 32 points 2 months ago (1 children)

I just noticed what the numbers are. It really is easy to memorize. So convenient.

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[–] Robust_Mirror@aussie.zone 23 points 2 months ago (2 children)

987654312÷123456789

Change the 21 at the end of the first number to 12 and its perfect. It was only ever 9 away.

[–] shekau@lemmy.today 12 points 2 months ago
[–] edgemaster72@lemmy.world 9 points 2 months ago* (last edited 1 month ago)

Witch! Begone foul demon, and take your dark sorcery with you!

[–] PattyMcB@lemmy.world 20 points 2 months ago

The funniest part is that some people will never understand the absolute crusade that some mathematicians might fight over this one day

[–] deegeese@sopuli.xyz 16 points 2 months ago (2 children)

I wonder if there’s a related infinite sequence which converges on 8?

[–] moonlight@fedia.io 21 points 2 months ago (1 children)

This sequence approximates an integer to arbitrary precision, not 8 specifically though, and never perfectly.

I tried it out using other bases, and the rule seems to be that doing this in base n results in n-2 with remainder n-1. So it doesn't ever actually converge, but the remainder becomes small very fast.

[–] match@pawb.social 11 points 2 months ago (2 children)

never perfectly

eyes you in binary

[–] deegeese@sopuli.xyz 9 points 2 months ago (1 children)

The sequence in base 2 is only 1/1.

Wonder how close base-16 gets.

FEDCBA987654321 / 123456789ABCDEF

[–] moonlight@fedia.io 10 points 2 months ago

Off by '1.82959E–16' !

[–] moonlight@fedia.io 4 points 2 months ago

Hmmmm.....

Edit: you can kinda think of it being 0, plus the 1/1 that would have ended up as a remainder in larger bases. In base 2, it just ends up being a full 1.

[–] Rusty@lemmy.ca 4 points 2 months ago

(n * 8 + 1) / n

[–] Hjalamanger@feddit.nu 14 points 2 months ago

9876543210987654321 / 1234567890123456789 = 8,0000000729000

[–] FooBarrington@lemmy.world 11 points 2 months ago (1 children)

You may call it an approxim8ion

[–] BodilessGaze@sh.itjust.works 3 points 1 month ago

gr8 m8, I r8 8/8

[–] expatriado@lemmy.world 5 points 2 months ago (1 children)
[–] moonlight@fedia.io 12 points 2 months ago

See my other comment, it's no coincide– there's a pattern. I would love to see an actual proof for it though, I don't know enough to say why it behaves that way.

[–] thedeadwalking4242@lemmy.world 5 points 2 months ago* (last edited 2 months ago) (2 children)

It contains the number 8 though. So how is that useful

[–] Opisek@lemmy.world 5 points 2 months ago

Well, simple. Jest substitute that 8 with the above approximation.

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