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Jul
26
comment How is the Fourier transform a geneeralization the the Fourier series?
@Mitsos - seems that I forgot the $n$, should be ok now
Jul
24
comment Notation of an infinite union
@vadim123 - whoops, I saw to many [infinite] sums this week :P
Jul
22
comment How prove : polynomial $P(x)=W^{\prime \prime}(x) +(W^\prime(x))^2$ have a real root.
How did you came up with this? What's the motivation?
Jul
17
comment For which integers $r$ is $\sigma ^r$ also a $k$-cycle?
You should at least describe your proof so someone won't repeat it
Jul
13
comment Prove that $\mathbb Z^n$ is not isomorphic to $\mathbb Z^m$ for $m\neq n$
How is it? It seems that (1,...,1) is not in the cyclic subgroup generated by this element. It seems that this cyclic subgroup is (0,...,0,Z,0,...,0)
Jul
13
comment Prove that $\mathbb Z^n$ is not isomorphic to $\mathbb Z^m$ for $m\neq n$
Can you prove the claim about the number of generators?
Jun
24
comment Worst case binary search
I'm not sure I understand, what is the data set? Is it all of [0,1]?if so it is infinite so we need to talk about that, binary search is defined for a finite collection. Also, it seems like you're thinking of searching in [0,1] with this method of eliminating halves of the interval each time, you can consider the binary representation of a number to estimate the number of steps needed for such a method
Jun
9
comment How to calculate $\log \log \log N$?
Well, how do you calculate log(N)? What is the time complexity of that? Why do you think that calculating your expression by calculating each logarithm separately is slow?
May
24
comment An example of a group such that $G \cong G \times G$
Oh. It's displayed wrong in the mobile site
May
24
comment An example of a group such that $G \cong G \times G$
I don't understand.. If H is finite for example it's not true
May
9
comment Homomorphisms and Groups proof
@danny $f(b^{2})=f(b\cdot b)=f(b)\cdot f(b)=f^{2}(b)$ . Now use induction
May
3
comment Do you know Legendre's conjecture ? Has it been proved?
Can't you just take epsilon to be small enough such that the difference between the expression with the exponent of 2 and the one with exponent of 2 plus epsilon is less then 1? If the claim holds for every positive epsilon this reasoning should show it holds for epsilon equals zero
May
2
comment Why is the zero polynomial not assigned a degree?
Increasing in what variable ?
May
2
comment Why is the zero polynomial not assigned a degree?
what about $+\infty$ ?
May
1
comment Find the splitting field of $x^6-2x^3-1$ over $\mathbb{Q}$.
Splitting field over what base field ?
May
1
comment Evaluating $\lim\limits_{n\rightarrow \infty} \frac1{n^2}\ln \left( \frac{(n!)^n}{(0!1!2!…n!)^2} \right)$
Did you try to cancel out some of the terms ?
Apr
25
comment Is a pattern proof?
No, this [post][1] contains many examples [1]: math.stackexchange.com/questions/514/…
Apr
25
comment Prove that this set is open
@drhab - I think you should keep it, it can be interesting for future readers as it is a confusing matter
Apr
25
comment Prove that this set is open
@drhab - It is prove! If $X=\Pi_{i=1}^{n}\mathbb{R}$ one can consider two topologies on $X$ - The product topology and the topology induced by the metric on $\mathbb{R}^{p}$. I proved that $A$ was open without relying on the fact that the two topologies on $X$ are the same since I assumed the OP does not know that
Apr
24
comment Topology, maps, continuity
@smits - then $f^{-1}(U)$ is closed. This condition is equivalent for the continuity of $f$