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• Post #4488925

  What's the correct interpretation this statement? "There exists a positive number 𝑥 such that for every positive number 𝑦, we have 𝑦²=𝑥." Is it ∃𝑥,∀𝑦[𝑦²=𝑥] or is it ∀𝑦,∃𝑥[𝑦²=𝑥] My (beginner) vote is for the first one ∃𝑥,∀𝑦[𝑦²=𝑥] #maths #quantifiers

• Post #4274103

  Have fun with Prolog! ... especially if you didn't enjoy it at university. book - https://www.amazon.com/dp/B0BTQ7P69H/ youtube - https://www.youtube.com/@prologbyexample/videos blog - https://prologbyexample.blogspot.com #prolog #gofAI

• Post #4274102

  This is an error in the author's solution, surely? (my working is here and says \[ 2^{2^{n+1}} =(2^{2^n})\times (2^{2^n}) \] https://numbertheorystepbystep.blogspot.com/2026/07/exercise-6312.html ) #maths

• Post #4274101

  for my next project I don't want to use github some people mentioned codeberg - but is that still a suitably ethical recommendation? are there other options? what I value/need: * will be around years from now * i can use it via a web browser to do the basics (upload content) * a macOS GUI tool would be nice but not crtical, I guess this means compatible with the git protocol * nice to be able to render common files in the browser eg pdf, png, * usable zero price option #githu...

• Post #4058220

  If an author writes a maths textbook with exercises, .... is someone else (me) allowed to write a book of solutions and publish it? Or does that break copyright? Or is reproducing the exercises considered "fair use" ? #maths #writing #publishing #copyright

• Post #4043360

  correction #maths #writing

• Post #4043290

  True: 6<2x<4 for all 3<x<2 False: 6<2x<4 for some 3<x<2 Why? I can convince myself the first is vacuously true. But why is the second false? #maths #logic

• Post #4038578

  X⇒Y is the same as "X is true only if Y is true" ... according to Tao Analysis I A.2. I still haven't settled this in my mind. It seems the wrong way around. Bur Tai says it takes some mental effort to see it. Is it obvious to you? How? #maths #logic

• Post #1764048

  Any recommendations for a *protetcive* sleeve for a macbook ? For years I used an Incase Icon with "tenserlite" which is just padding around the egde to protect against falls hitting the edge first. The magnet appears to have weakened, and the laptop keeps slipping out and hitting the floor. Can't get these any more it seems - so what do people recommend today? #apple #macbook #macbookpro #sleeve #tech

• Post #1666324

  currently watching this nice video on blue noise by @demofox https://www.youtube.com/watch?v=tethAU66xaA #bluenoise

• Post #1666323

  Perhaps Tim accidentally resigned because he got confused by Liquid Glass. #liquidglass #apple #timcook

• Post #1666322

  𝗠𝗮𝘁𝗵𝘀 𝗣𝗿𝗼𝗼𝗳𝘀 𝗶𝗻 𝗟𝗲𝗮𝗻 - 𝗙𝗶𝗿𝘀𝘁 𝗦𝘁𝗲𝗽𝘀 You don't need to be a PhD to write simple maths proofs in Lean. This course takes you from a complete beginner, and gives you enough confidence to read and write simple proofs. Each chapter has one exercise, designed to build confidence, not destroy it! youtube: https://www.youtube.com/@LeanFirstSteps/videos free content: https://leanfirststeps.blogspot.com/p/contents.html book: https://www.amazon.com/dp/B0DWHS1RDJ #leanprover #education #maths

• Post #1666320

  I remember seeing a few of these back in the day ... https://en.wikipedia.org/wiki/2600%3A_The_Hacker_Quarterly --- "The magazine's name comes from the phreaker discovery in the 1960s that the transmission of a 2600 hertz tone – which could be produced perfectly with a plastic toy whistle given away free with Cap'n Crunch cereal, discovered by friends of John Draper – over a long-distance trunk connection gained access to operator mode, and allowed the user to explore...

• Post #1666319

  I'm now learning how "indices" of primitive roots can help in the same way taking logs can help: ---- Determine the least non-negative residue $x$ such that \[7^{100}6^{100} \equiv x \pmod {17} \] my solution: https://numbertheorystepbystep.blogspot.com/2026/04/exercise-639.html #maths #numbertheory

• Post #1666318

  Doing an exercise to show the following has no solutions. \[x^3 \equiv 89 \pmod {197}\] We can use a proposition - see attached image. Question: why does the author's solution NOT first establish that 𝑛=197 has a primitive root? Surely the proposition is only true if 𝑛 has a primitive root. #maths #numbertheory

• Post #1361211

  How do you change the default font for LibreOffice spreadsheet app Calc? This question illustrates how ux and ui design still has a way to go in major open source projects that seek to compete with popular proprietary software. 1. The method is not where you'd expect it. 2. It doesn't change the default for Calc, only for that file. 3. Normal users shouldn't have to mess with "templates" and give them "specific names". 4. If the above is wrong, that adds weig...

• Post #1080145

  I've finally removed MS Office. I've been using LibreOffice for years, but I kept MS Office around for "business tasks", ... filling in forms and spreadsheets sent to me, where a formatting screw up would mean actual costs and disadvantages. LibreOffice is still not giving me full confidence - that UI is a factor, but I'm going with it. Fingers crossed. #libreoffice #opensource #tech