114,735 reputation
7106211
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 2 years, 1 month
seen 9 hours ago

I did study math and had a knack for it, but I am sooo out of that business now ...


May
21
revised About the property of $m$: if $n < m$ is co-prime to $m$, then $n$ is prime
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May
21
answered About the property of $m$: if $n < m$ is co-prime to $m$, then $n$ is prime
May
21
comment logic question inferences
"Primae sunt Barbara, ..."
May
21
comment A family of sets such that the each subfamily has a different union
"Every pairwise disjoint family $\mathcal A$ satisfies this condition" - No, we must not have $\emptyset$ itself in the family.
May
21
answered A family of sets such that the each subfamily has a different union
May
21
answered Proof of the uniqueness of maximal ideal
May
21
comment Coset of W containing $v$ is a subspace of $V$ iff $v \in W$
Argumentation using coset properties might be simpler. For $\Rightarrow$ I'D simply write that if $v+W$ ia a subspace, it contains $0$, as does $0+W$, hence $v\in v+W=0+W=W$. For $\Leftarrow$ similary: $v\in W$ implies $-v\in W$ implies $0\in v+W$ imlies $v+W=0+W=W$. - Otherwise wour proof is fine, except that it uses the unjustified assumption that $2$ is invertible in the ground field.
May
21
comment Must a complex power series *fail* to be convergent somewhere on its circle of convergence?
I think the power series for $\sqrt {z+1}$ should converge on all of $S^1$, but it cannot extend beyond $z=-1$.
May
21
revised Is it possible to make a regular 3-polygon by selecting $3$ points in $S$
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May
21
answered Is it possible to make a regular 3-polygon by selecting $3$ points in $S$
May
21
comment Probability of two random n-digit numbers dividing each other
@Prism Yes, these were found by brute-force counting. More early terms of the sequence can be calculated like that, but it takes longer and longer and gets more and more boring.
May
21
revised Probability of two random n-digit numbers dividing each other
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May
21
awarded  Constituent
May
21
answered Is the function identically zero?
May
20
comment Show $C\geq \mathrm{max}\left \{ A,B \right \}$.
@AjmalW Erm, what do you know about the radius of convergence and how to compute it? That $\limsup$ is precisely the reciprocal of the radius of convergence (Cauchy-Hadamard) and I know of no other formula that works for general power series.
May
20
revised Probability of two random n-digit numbers dividing each other
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May
20
answered Probability of two random n-digit numbers dividing each other
May
20
revised Show $C\geq \mathrm{max}\left \{ A,B \right \}$.
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May
20
comment Show $C\geq \mathrm{max}\left \{ A,B \right \}$.
Do you know what role that $\limsup$ plays for the radius of convergence?
May
20
comment What is the name of a game that cannot be won until it is over?
@joriki We might consider games with infinite decision trees where all leaves (as they are in finte distance from the root!) are lost positions. The only way to win seems to be to follow an infinite path in the tree. However, there is no leaf along that path, so there is no winning at all. - Or as WOPR would put it: "Shall we play?" (TicTacToe or Global Thermonuclear War)