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 Feb 9 comment Which derivatives are eventually periodic? Try a composition, like $f(x) = e^{-x^2}$... Feb 7 comment Why don't infinite sums make any sense? @EricStucky: I don't know if you noticed, but the crux of the OP's trouble is the part that says "...occasionally revising numbers later to the right of the decimal". I tried to show how to look at the same problem in a way that doesn't require that, thus reducing it to something that the OP would hopefully be comfortable with. If that isn't the case then I guess we'll see a comment to the contrary. Feb 7 answered Why don't infinite sums make any sense? Feb 1 comment How could we define the factorial of a matrix? +1 to get you to the 50th vote just because the first paragraph itself just blew my mind. Thank you for this! Jan 31 comment Resources to understand real world usage of linear algebra There's also spectral graph theory. Jan 20 comment Are j and k on different imaginary planes than i? Wasn't the downvoter, but I don't really understand what you're saying about the matrices. How did you turn a complex number into a matrix?! Jan 16 answered If squaring a number means multiplying that number with itself then shouldn't taking square root of a number mean to divide a number by itself? Jan 14 comment Notation of the second derivative - Where does the d go? It's because the dx is "in parentheses", so to speak. Jan 9 comment Is there a symbol for plus and minus as opposed to plus or minus? @MarianoSuárez-Alvarez: Yes I agree that I don't have any problem understanding the downvotes that came after the modification to the answer, but those are only the ~3 or so since 4 hours ago. I was talking about the ~9 or so other downvotes (the answer had zero net votes when I wrote my comment, and while I didn't check the number then, I don't expect it has received many/any upvotes since then); I do have a problem understanding those and I think they were unfounded knee-jerk reactions like I talked about earlier. Jan 9 comment Is there a symbol for plus and minus as opposed to plus or minus? @MarianoSuárez-Alvarez: I agree that wasn't the best way to phrase it, but goblin does have a point. It's a genuine problem. I have empirically seen similar reactions myself; for whatever reason, some people here do have a habit of knee-jerk downvoting answers merely because of unfamiliarity, and it's awful. I'd even go so far as to say that right now I can almost guarantee you that some of the downvotes this answer is receiving at this point are because people don't like the comments, and have nothing to do with the merits of the answer itself. Jan 9 comment Is there a symbol for plus and minus as opposed to plus or minus? @NateEldredge: A couple things: (1) Could you explain what interpretation the professional mathematician does assign to the plus/minus symbol? Surely they've seen it before, right? How do they interpret it when they come across it? Or is their only standard response to burn the paper in flames without any attempt to understand it and then move on? (2) Could you also explain why you think the question and answers on this page should be directed toward the "professional mathematician" in the first place? Are you sure you're not confusing this website with MathOverflow? Jan 8 comment Is there a symbol for plus and minus as opposed to plus or minus? +1. @NateEldredge: I would argue that your aversion to this interpretation is a bit unfounded; the typical "or" interpretation is just a colloquial version of the multiset interpetation. It's just that simply no one called it a multiset before, but that's what it is. How else would you formally define it? Jan 8 answered Is there a symbol for plus and minus as opposed to plus or minus? Jan 6 revised Is this a way to prove there are infinitely many primes? added 2 characters in body Dec 27 revised Does a smooth “transition function” with bounded derivatives exist? Simplified it further for those who find this form more useful Dec 24 awarded Good Question Dec 24 comment Why is the rational number system inadequate for analysis? My first reaction is "is the difference actually consequential?" Because all that seems to happen is that theorems turn from "there exists a p such that f(p) = 2" into "there exists a sequence p[k] that approximates f(p[k]) = 2 arbitrarily closely"... so why is that such a big deal? Limits are all about having arbitrarily close approximations anyway, which we still have... Dec 20 comment Prove that the limit of $\sqrt{n+1}-\sqrt{n}$ is zero @HenryW: I mean do you try it because you're used to it, or do you try it because you have a reason to believe it might work? Because honestly I don't intuitively understand why it should work. Dec 20 comment Prove that the limit of $\sqrt{n+1}-\sqrt{n}$ is zero Can you explain how you realized you're supposed to use conjugates? It's not really enlightening otherwise. Dec 19 comment what does it mean for a function to be riemann integrable @AndrewD.Hwang: Maybe it was to avoid talking about area cancellation...