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bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 2 years, 3 months
seen 6 hours ago

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


Dec
12
revised Help with Random High Card Probability Question
added 457 characters in body
Dec
12
revised Help with Random High Card Probability Question
edited tags
Dec
12
answered Help with Random High Card Probability Question
Dec
12
answered Help explain the end of this proof for infinitely many primes?
Dec
12
answered Is $S^1$ homeomorphic to $\mathbb{R}P^1$?
Dec
12
comment Students who see ears of another student
Very elegant and direct. I was still doing the details for a convoluted induction proof that, more generally, $m\times n$ needs $\min\{m,n\}+2$. Using your nice line-counting argument, this generalized result also follows at once: If wlog. $m\ge n\ge 2$, then each line has at most $m-1$ students and from $(m-1)(n+1)<mn$ we see that at leat $n+2$ lines are needed (and as dropping columns from the left in your illustration shows, $n+2$ lines suffice).
Dec
11
answered Existance of an analytic funtion satisfying some condition
Dec
11
comment Is there a general method to find if ideal is maximal
In what form would you produce the ring and the ideal as input to such an algorithm?
Dec
11
answered Applying math knowledge
Dec
11
comment Does there exist a unique closest natural number to each rational number?
The claim is wrong. For $x=\frac32$, there is no unique closest natural number
Dec
11
answered Show that the number $n$ is divisible by $7$
Dec
11
comment How to find solutions of coin weighing problems with multiple light coins and prove optimality
This may be of interest (but deals with the case that $k$ is unknown, and optimality is unknown - in fact, unlikely)
Dec
10
answered How to show if it is irreducible
Dec
10
answered Is Pythagore's Theorem easy ?
Dec
10
comment Which number is odd one out in set $\{5, 7, 11, 29, 41\}$
I can't make up my mind. The property $k^2-k+n$ is prime for all $0\le k<n$ is valid both for $n=5$ and for $n=41$ ...
Dec
10
comment A bounded sequence of a complete Metric Space
... with $d(a,b):=\sup|a_n-b_n|$ as metric and $a_n,b_n$ being real sequences?
Dec
10
comment If $1$ was a prime, could it be possible for the prime factorization of any number to go on forever?
"If $1$ was a prime" is as good a premise as "if pigs could fly".
Dec
10
comment Rules for translating quantifiers to set operations?
In the light of application to measure theory, we may assume that the OP is mostly interested in countable unions/intersections, so in quantifiers retricted to countable sets, as in $\forall x\in\mathbb N\colon P(x)$, $\exists x\in\mathbb N\colon P(x)$.
Dec
10
comment Is $f$ continuous if for every $p$, there is a sequence $p_n \to p$ such that $f(p_n) \to f(p)$?
Your proof is fine. BTW, the claim would still be false if one required that the sequences be injective: Consider $\mathbb R\to \mathbb R$, $x\mapsto \begin{cases}1&\text{if $x\ge 0$}\\0&\text{if $x<0$}\end{cases}$. Then for any $p$, the sequence $p_n=p+\frac1n$ exists with $f(p_n)\to f(p)$.
Dec
10
answered There is no increasing positive sequence $(u_{n})_{n}$ with this condition: $(u_{n}^{(1/n)})_{n}$ is decreasing