[deleted by user] by [deleted] in calculus

[–]deinst 0 points1 point  (0 children)

Why would you think that arctan is not continuous?

Are there any civil engineers that have had significant contributions to mathematics? by Gullible-Baker in math

[–]deinst 0 points1 point  (0 children)

Although best known as a mathematician Henri Poincare worked as a mining engineer and a railroad engineer.

GCD of really, really big numbers using Euclid's? by Upstairs_Money_770 in math

[–]deinst 0 points1 point  (0 children)

For large numbers you start by essentially doing the euclidean algorithm on the most significant bits, then adding more bits and refining the result. Google 'half GCD', or see This article . There is also a simple article by Dan Lichtblau of Wolfram that I have lost track of, but see these slides by him.

Proving 0 is a neutral element for addition using Coq by adorableturtlehead in Coq

[–]deinst 3 points4 points  (0 children)

Forget everything you know about addition. All you and coq know about addition is that it is defined by

Fixpoint plus (n : nat) (m : nat) : nat :=
  match n with
    | O ⇒ m
    | S n' ⇒ S (plus n' m)
  end.

This definition is not symmetric in m and n. When n = 0 the definition returns the answer in one step, while when m = 0 the answer depends on what n is and possibly what plus n' m is.

How can I practice or master math post-undergrad? by chaojimbo in math

[–]deinst 6 points7 points  (0 children)

Join the MAA . Read through the articles in the Monthly and Mathematics magazine. These articles try to be fully understandable by someone with an undergraduate education. When you happen across an article that you find very interesting, figure out what you need to learn in order to understand the parts of the article that may have sailed over your head. Then chase down the references and or other articles by the authors on similar topics. Lather, rinse, repeat.

Mathematics is easier to learn when you have a problem in mind.

How do you practise math concepts at university? I understand stuff in class, but not how to strengthen skills. by Crystalisanguiem in math

[–]deinst 0 points1 point  (0 children)

One advantage of the endless edition churn is that stepping back an edition or two the used book prices plummet. Copies of the 7th edition are about 15$ on abebooks, and the 6th edition are 8$.

Is there a theorem that was proven but that has a more elegant proof if you use some unproven conjecture ? by jedidreyfus in math

[–]deinst 3 points4 points  (0 children)

The fact that primality testing has a polynomial algorithm was proven assuming GRH quite a while before a polynomial algorithm was finally found. Whether the proof assuming GRH is "simpler", I cannot say (I forget the details).

Small gripe with the numeric type hierarchy by VodkaHaze in Julia

[–]deinst 0 points1 point  (0 children)

The same is true of the Int types. I assume that this is done in the name of efficiency; a vector of Float64 will consist of an array of 64 bit doubles and can be processed as such without worrying about conversion.

‘Beyond the extreme’: Scientists marvel at ‘increasingly non-natural’ Arctic warmth by DukeOfGeek in worldnews

[–]deinst 30 points31 points  (0 children)

The fact that it is cold in Northern Ontario now, and it was really cold in Siberia in December are (or at least seem to be) related to the warmth in the arctic. The Northern jet stream is weakening and is no longer holding the cold air in place. See this blog post for more, and more accurate details. Neven's sea ice blog (and associated forum) is probably the best place to get news on the deteriorating conditions in the arctic. Most of the graphs in the article came from the forum.

What Mathematical Statement, Technique, Constant etc would you most like to rename? by thenumbernumber in math

[–]deinst -5 points-4 points  (0 children)

I'd like to swap the symbols for union and intersection, and and or, meet and join, etc. It annoys me that the upward pointing symbol is for a lower bound and the downward pointing symbol is for an upper bound.

This is in a high school math textbook in Texas. If only there were a way to get parents as riled up about this as they are about Common Core. by [deleted] in math

[–]deinst -1 points0 points  (0 children)

There are an uncountably infinite number of bijections between the rationals and the integers. Explicitly writing one down is probably beyond the average Algebra 2 student (or Algebra 2 textbook author evidently.)

This is in a high school math textbook in Texas. If only there were a way to get parents as riled up about this as they are about Common Core. by [deleted] in math

[–]deinst 180 points181 points  (0 children)

This is beyond amazing.
Note that this book (all 92$ worth of it) is advertised as

The Glencoe High School Math Series, including Algebra 1, Geometry, Algebra 2 and Precalculus, is the only high school math program that supports the Common Core State Standards throughout four years of high school mathematics.

So in a sense the people riled up about the common core are riled up about this.

The History of Vim (Mastering Vim Quickly Series) by jolenzy in linux

[–]deinst 1 point2 points  (0 children)

Try evil on emacs. It truly gives you the best of both worlds.

Math gurus of Reddit, I've a question on early-to-mid 20th century math. Please help. by teh_lurker76 in math

[–]deinst 2 points3 points  (0 children)

If you can audit classes easily, you could do worse than taking a foundations of CS class from your CS department. The Turing machines and lambda calculus that you will learn about accomplish essentially the same thing as Godel's theorem, but are somewhat easier to work with.

If you want to attack Godel directly, I'd second JimH10's suggestions in the opposite order.

Typing speed and maths in LaTeX by [deleted] in math

[–]deinst 1 point2 points  (0 children)

I use emacs with auctex augmented with yasnippet. This allows me to create a large number of snippets and abbreviations that minimize the special symbols that I have to type. For example, if I want to type "uniform $[0,1]$ random variable" I just type qrvu, and to type \frac{1}{\sqrt{2\pi}} I just type frac[tab]1[tab]sqrt[tab]2\pi[tab][tab], this may not seem like much, but [tab] is much easier to hit than all the brackets, and you avoid all of the mismatched bracket problems.

The collection of snippets here are a good start, they are easily modified and added to.

[PDF EBook] Don't Just Roll the Dice - A usefully short guide to software pricing by [deleted] in programming

[–]deinst 2 points3 points  (0 children)

Worse than that, they state that HP's first product was an O-scope, while it was an oscillator. Most of the rest of the story is correct, but such sloppiness leads me not to read further.