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yori

Re:Product of Negatives (2010) on Sunday March 01, 2020 @02:28PM (#22458675)
> You cannot work backward by assuming the field axioms (which are unfortunately named because they are not axioms at all but properties) to derive the definition o the field operators.

Of course, when we say they are field axioms we mean those properties hold true for the elements of the field. If you see those properties, they talk about distributivity over the elements of the field and additive inverses of the elements also belong to the field, so the distributivity automatically applies to additive inverses too.

After that with a little algebra, "product of additive inverses of two elements is equal to the product of the two elements" comes out as a result (not a definition).

Of course, by "product" we mean whatever * represents. It is not necessarily the multiplication operator we see in numbers.

Re:Product of Negatives (2010) on Sunday March 01, 2020 @01:33PM (#22458307)
> If we'd chosen some other definition of multiplication, a lot of the "intuitive" properties of multiplication that hold over the natural numbers (such as the distributivity of multiplication over addition and subtraction) would no longer be true over the integers.

This is backward reasoning. The chosen definition of multiplication is not to keep things "intuitive". If you start with the field axioms, the chosen definition of multiplication is pretty much dictated by the axioms. If you choose another definition of multiplication, you would end with contradictions like 1 = 0 and such nonsense! And mathematicians abhor contradictions!

"Product of additive inverses of two elements is equal to the product of the two elements" is dictated by the field axioms in all fields.

Re:Product of Negatives (2010) on Sunday March 01, 2020 @01:26PM (#22458260)
Not every arithmetic property needs to be proved from Peano axioms. One can but it is tedious and unnecessary. A much better starting point is the set of field axioms where the distributivity property is already available as an axiom.

The assumptions made in the article are perfectly fine as per field axioms. Granted it would have been nicer if distributivity over addition was used instead of distributivity over subtraction. But it is not a big leap to derive distributivity over substraction from field axioms by distributing multiplication over a positive number and the additive inverse of another positive number.

Wherever you see an assumption made about negative number, just mentally replace it with additive inverse of a positive number and you would be fine.

Re:Product of Negatives (2010) on Sunday March 01, 2020 @07:38AM (#22456636)
Like mentioned in another comment on this thread, the assumptions are well known field axioms. They form a good starting point.

And why start with Peano axioms? They seem like a bad starting point because it would take pages upon pages of proof and it won't easily extend to other algebraic structures like rings and fields.

Re:Clumsy Equations (2010) on Saturday February 29, 2020 @06:32AM (#22450102)
> There is no simple way to solve this equation. I had to resort to using the Lambert W function to solve this.

How do you know when to use Lambert W function?

Re:An Intuitive Guide to Linear Algebra (2012) on Wednesday February 26, 2020 @02:16AM (#22421035)
What your parent comment meant was that it is not possible to learn well from typical blog posts like this that try to condense the subject into a 3000 word article. Of course, if you copy-paste the content of a book into a blog post, then parent comment's point no longer applies.
Re:Principles of Icon Design on Thursday February 20, 2020 @08:02AM (#22374754)
Off-topic question: I see a lot of new posts coming from .cc websites. What is the appeal that .cc provides? Is it that the content is released under Creative Commons? That's not the case here. What kind of messaging or symbolism or underlying meaning one is aiming for when they are going for a .cc domain?
Re:BBC Micro Bot on Thursday February 20, 2020 @04:33AM (#22373849)
Example code on the website:

  10 MODE 2
  20 COLOUR RND(7)
  30 PRINT "HELLO WORLD"
  40 GOTO 20
Happy to see "colour" spelled the English way. :-)
Re:Stop Using Encrypted Email on Wednesday February 19, 2020 @11:52PM (#22372766)
Yes, I didn't get the usage of the term "LARP" in this context too. It comes off as rude and condescending to both LARPers and email users. I am not sure the term fits appropriately in this context. All LARPers are aware that they are role playing in a game, not the real world, and they do not pretend otherwise.
Re:I Add 3-25 Seconds of Latency to Every Site I Visit on Thursday February 13, 2020 @01:06PM (#22319870)
> Withdrawn mostly from Reddit in favor of early 2000’s style forums that I pay money for and HN

What are the names of these early 2000's style forums? I would like to join them too.

Re:Why we need a book about naming on Thursday February 13, 2020 @08:48AM (#22317668)
"There are only two hard things in Computer Science: cache invalidation and naming things."
Re:How to Tell a Mathematician You Love Them (2017) on Thursday February 13, 2020 @08:46AM (#22317651)
What's the deal with Hagoromo chalk? Why is it a romantic gesture?
Re:Usenet – Let's Return to Public Spaces on Thursday February 13, 2020 @08:43AM (#22317636)
> Despite the english name of the website, it's a german page, so no use in linking it here I suppose.

No, please do link it here. First, there are many Germans here who would appreciate it. Second, people like me who cannot read German can still auto-translate the page to English and read it.

Re:Usenet – Let's Return to Public Spaces on Thursday February 13, 2020 @08:38AM (#22317606)
Has Usenet really died? I still see many active newsgroups with posts appearing daily.
Re:Show HN: Discover the World of Mathematics on Wednesday February 12, 2020 @11:57PM (#22315424)
Are you rendering the LaTeX on server-side or on client-side using JavaScript? I am asking these questions because I find MathJax code in your website:

  <script type="text/plain" cookie-consent="strictly-necessary">
    window.MathJax = {
      tex: {
        inlineMath: [['$', '$'], ['\\(', '\\)']]
      },
      svg: {
        fontCache: 'global'
      }
    };
  </script>
  <script type="text/javascript" id="MathJax-script" async
    src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js">
  </script>
Re:Plasma 5.18 on Tuesday February 11, 2020 @10:46AM (#22299348)
I use XFCE. Are there any good reasons to switch to KDE? Honest question.
Re:Show HN: Discover the World of Mathematics on Tuesday February 11, 2020 @05:28AM (#22297412)
Are you using MathJax to display the equations? Why do I not get the MathJax context menu when I right-click on the equations?
Re:Becoming a blockchain developer on Monday February 10, 2020 @08:17AM (#22288814)
I provided a cryptographic proof that does not require blockchain.
Re:Becoming a blockchain developer on Monday February 10, 2020 @08:05AM (#22288731)
How about this? Write your bug report. Sign the bug report with your private key. Anonymously publish the bug report, the signature and the public key. Later when required, prove that you wrote the bug report by using your private key to sign a new message or a challenge message sent by any challenger.
Re:Systemd Home Directories on Monday February 10, 2020 @07:06AM (#22288400)
Why did the sessions disappear? Can you explain more about it?
Here's a good one: https://susam.in/

Stumbled on this when his domain was hijacked accidentally due to an anti-botnet operation and his post about it came on HN (check the "Sinkholed" post). Since then I've subscribed to his blog, read the older posts and enjoyed the newer posts too.

He mostly posts about technology and mathematics. The reason why I got hooked to this blog is that they are mostly about offbeat topics that I wouldn't normally come across on my own. So there is something new to learn from every post. And they are very well written with great attention to detail.

Re:Ask HN: What Skills to Acquire in 2020? on Tuesday February 04, 2020 @11:26AM (#22237436)
Do you really mean plain old Docker or do you mean Docker Swarm as well?

I think Docker Swarm is necessary in the absence of Kubernetes to ensure that the correct number of replicas are running on your cluster. It would help with automatically spinning up new replicas when a few nodes go down, changing the number of replicas on the fly, etc.

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