# Recent content by TheFurryGoat

1. ### Subsequences and sequential compactness

I agree with this. I got carried away and forgot what was to be proved.
2. ### Proving (a weaker form of) Bertrand's postulate

woops, sorry, got mixed up with my thoughts, you're right.
3. ### Proving (a weaker form of) Bertrand's postulate

The problem here is, that you use the fact that if p|(n+M) \text{ and } p|n \Rightarrow p|M. But this doesn't cover all the possibilities, namely if p\not|n \text{ and } p\not|M \text{ but } p|(n+M), as micromass pointed out.
4. ### Proving (a weaker form of) Bertrand's postulate

For any k\geq 2 choose n to be the product of all prime numbers \leq k. Then \{p\in\mathbb{P} : p < n, p \not |n \}=\emptyset. So M need not exist, if I'm not mistaken.

No problem. I suspect that we have all made these kinds of mistakes, it often happens to me when the problem statement is complicated. :)
6. ### Subsequences and sequential compactness

Yeah, that's the part that caught me as well. I remember seing your function somewhere also, it seems to be the most straight forward. The function sequence I had in mind was f_n(x) = \begin{cases} n\cdot x & \text{if} \; \; 0 \leq x < \frac{1}{n} \\ 1 & \text{if} \; \; \frac{1}{n} \leq x...
7. ### Legendre polynomials

Under the orthogonality section in the wikipedia article on Legendre polynomials, you find the identity \displaystyle \frac{d}{dx}\left[(1-x^2)\frac{d}{dx}P(x)\right] = -\lambda P(x) where the eigenvalue \lambda corresponds to n(n+1). I suppose P(x)=P_n(x) for any n, but I'm not sure though...
8. ### Subsequences and sequential compactness

Mayby I'm confused with the notations but I thought that \displaystyle d_{\infty}(f,g)=\sup_{x\in[a,b]}|f(x)-g(x)|<\epsilon meant uniform convergence, since doesn't this mean that \forall x\in[a,b]:\ |f(x)-g(x)|<\epsilon?

Did you forget x(t) from the integrand?
10. ### Subsequences and sequential compactness

For the last problem, try to find a sequence of continuous functions that converges to a non-continuous function. I have one in mind, but haven't thought of the details yet. Consider piecewise functions... edit: Sorry, the path I suggested might not lead you anywhere. It seems that if a...

You have defined u(t)=0 when t<0 and x(t)=e^{-100t}\cdot u(t).
12. ### Legendre polynomials

What properties do you know about Legendre Polynomials? If you can use the orthogonal properties that are listed in the article on Legendre polynomials in wikipedia, then integration by parts should do the trick.
13. ### Subsequences and sequential compactness

I suppose you would prove it by the same reasoning as you'd prove that the sequence \{n\}_{n\in \mathbb{N}} diverges, reductio ad absurdum using the definition of convergence to get a contradiction.
14. ### Subsequences and sequential compactness

What is the definition of \{ x_n \} converging to x in X? And remember (\forall n\in \mathbb{N})\ (\exists n_k \in \mathbb{N}) : n_k\geq n.
15. ### Markov Chains and Limit question : Where have I gone wrong?

If it is calculated like I suspect it is, then you will get a satisfying answer. So first we want to find out what f_3^n is when n\geq 3: f_3^n = \displaystyle \frac{1}{2}\cdot1\cdot\left(\prod_{k=3}^{n-1}\left(\frac{k}{k+1}\right)^a\right)\cdot\left(1-\left(\frac{n}{n+1}\right)^a\right) =...