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seen Nov 21 at 7:38

Nov
9
comment 1/∞ is 0 or infinitesimal?
1/x as x approaches infinity is slightly different to saying what is 1/infinity. The limit is indeed 0, but the fraction 1/inf doesn't really make sense mathematically, but I guess I would describe it as infinitesimally small if I had to.
May
23
comment Algebra: What allows us to do the same thing to both sides of an equation?
Isn't it obvious? If quantity A is the same as quantity B, then if you do something to A, it is no longer the same as B, unless of course you do the same thing to B as well. For example if A = 5, and B = 5, then A + 1 = 6, and B+1 = 6. So if A = B, then A+1 = B+1
May
22
comment Easiest way to prove integral of $e^{ikx}$ is $\delta(k)$
@markleeds, unfortunately that answer makes use of the fourier theorem, but I am trying to use the above integral to prove the fourier theorem.
May
21
comment Easiest way to prove integral of $e^{ikx}$ is $\delta(k)$
@Mathlover, I'm asking how do you know that the integral of g(x) from -e to e is 2pi. You've stated it but haven't proven it, and this is the only step in the proof I don't understand.
May
21
comment Easiest way to prove integral of $e^{ikx}$ is $\delta(k)$
@Mathlover, I struggle with the last part of that proof. I can't understand the jump from lim sin(ax)/x = 2pidelta(k). How can we prove the limit is 2pidelta(k)?
May
21
comment Easiest way to prove integral of $e^{ikx}$ is $\delta(k)$
@Mathlover, thanks
May
12
comment Prove that $u(x,t)=\int_{-\infty}^{\infty}c(w)e^{-iwx}e^{-kw^2t}dw\rightarrow 0$ if $x\rightarrow \infty$
proofwiki.org/wiki/Riemann-Lebesgue_Lemma
Apr
7
comment How many ways to add to 21?
@NikhilMahajan,I want to know the process for answering this particular question. Full working out is expected from a good answer, as demonstrated by the accepted answer, hence I do not need to specify in the question that I want working to be shown.
Apr
7
comment How many ways to add to 21?
No this isn't homework, and I know the answer is 880, but what is the process to figure it out?
Apr
7
comment A proportionality puzzle
you misunderstood my point. You said that they clearly round up because 5/2 is rounded up. In fact most countries will round up 5/2 but this doesn't mean they will clearly round up 10/3. Therefore if it is given that they round 5/2, it is no indication that they will round up 10/3.
Apr
7
comment A proportionality puzzle
The fact 2.5 rounds to 3 doesn't mean that 3.33 rounds to 4, since most mathematicians will round up .5 and greater, but will round down anything less than .5
Oct
2
comment Surprising identities / equations
How is this formula not immediately obvious?
Sep
29
comment closed form $f_n=\sqrt{2f_{n-1}}$ ?
So f_1 = 2^(1 + 3/4) ?, but I thought f_1 was 2^(1/2)
Sep
29
comment Surprising identities / equations
This topic seems very intriguing, so thanks for posting +1.
Sep
28
comment Surprising identities / equations
@DanielV, it does lead to a paradox. The sum from 1 to infinity of 2^k = 2 + 2 + 2 + 2 etc. = -1 (our assumption). Now 2 = 1+1. Therefore 1 + 1 + 1 + 1 + 1 = -1. But the sum from 1 to infinity of 1^k = -1/2.
Sep
28
comment Surprising identities / equations
How can the sum from 1 to infinity of positive integers lead to a negative number?
Sep
11
comment Blue eyes: a logic puzzle
@IttayWeiss, what is an example of a harder logic problem?
Feb
6
comment Find a function that that makes the value of this improper integral equal to 1.
Thanks for your answer.
Feb
6
comment Find a function that that makes the value of this improper integral equal to 1.
I wasn't sure about the title. Please feel free to correct.
Feb
1
comment How is this linear 2nd-order ODE solved?
My solution accidentally solved for equation (11) instead of (14) oops