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Jan
27
comment Is there a notation for being “a finite subset of”?
That's soooooo set-theoretical notation!
Jan
27
answered Is there a notation for being “a finite subset of”?
Jan
27
comment Is there a notation for being “a finite subset of”?
@SteveJessop No. $<\omega$ is not better unless you're a set theorist. As you note yourself, $|A|<\infty$ is the most standard way of writing down that $A$ is finite, if you don't like "$A$ finite". That's what I would actually prefer myself: $A\subset B,\quad A \text{ finite}$.
Jan
21
comment Can you be 1/12th Cherokee?
@SteveJessop I know. At the same time, it's needed to say that the coins are not $100$ but rather something like $40000$, so the mean deviation is $\sim200 = 0.5%$. I just wanted to point out that it's not $23$. On the other hand, this means that you can get very precisely $1/12$ of Cherokee genes even with 2 or 3 generations considered. However, this model is far from what people have in mind with "I'm $1/8$th Cherokee", right?
Jan
21
comment Can you be 1/12th Cherokee?
@SteveJessop Needed to say: There's re-combination going on, so you receive 25% of each of your grandpa's DNA. (I'm not 100% sure on this, and a biologist should rather confirm my statement. Still, this is how I understood re-combinations.
Jan
18
answered Bijection between sets of ideals
Jan
6
comment How to stop forgetting proofs - for a first course in Real Analysis?
My favourite quote to the statistics teacher during the exam: "Excuse me, Sir, I don't remember the statement, but if you help me with it, I'll surely manage to show you the proof." Because the basic idea was that the theorem hypotheses need to be used in the proof, and that was usually enough to think out the steps.
Dec
23
comment Do we really need reals?
However, you can argue that computable numbers have sufficient completeness properties: Each computable sequence of computable numbers has a computable limit.
Dec
18
awarded  Caucus
Dec
18
comment What is the “fastest” increasing function that's useful in some area of math?
@KlasLindbäck Please note what has been said before: Dirac's delta function does not even answer the problem: it's not a function, nor it is growing. I don't see why this answer deserves +2. IMHO the answerer should have enough judgement and delete the answer.
Dec
18
comment What is the “fastest” increasing function that's useful in some area of math?
@MJD The blog article is a perfect thing for a lecture to high school students! I really love the game that is presented there at the beginning :) (btw, (x->9^(9^x))^(9^(9^9)) (9) would be my try :) )
Dec
2
awarded  Critic
Nov
20
comment Why do proof authors use natural language sentences to write proofs?
@artem But that's partly the beauty of a non-formal proof! If you understand the proof, seeing that "showing that $2p-n>0$ is necessary" is straighforward. And if you don't understand the proof, adding this information wouldn't help.
Nov
13
comment Why is the absolute sign needed in the definition of a bounded function
Well, or that $f(\operatorname{def} f)$ is a bounded set? :)
Oct
27
comment Dividing tournament into “equal” groups
The world tournament is well established in the graph theory, and is connected to "each plays each" type of a game: en.wikipedia.org/wiki/Tournament_%28graph_theory%29
Oct
24
awarded  Curious
Oct
23
accepted Is this enough to prove a homeomorphism? — inverse on a dense subset
Oct
23
comment Is this enough to prove a homeomorphism? — inverse on a dense subset
Yeah, I just realized that the problem is eventually simple, and all that needs to be said is that continuous image of a compact is a compact. Thanks for your help anyways for sure!
Oct
23
comment Is this enough to prove a homeomorphism? — inverse on a dense subset
@JohnZHANG Sorry I was not clear. I do have a proof that in my particular case, the 3rd item is true.
Oct
23
asked Is this enough to prove a homeomorphism? — inverse on a dense subset