104,968 reputation
694190
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 1 year, 10 months
seen 4 hours ago

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


6h
answered Checking a formula works for many numbers
6h
comment Where to post discovered formulae?
I think arxiv, while having a ... wide range of authors, still requires some endorsements/recommendations before you publish, don't they?
7h
comment Algebraic Proof of Sum of Exponential Powers is Product of Exponentials
... but the derivative tricks are much more fun
7h
comment Where to post discovered formulae?
@capturographer Publication need not be in a book, an article in a peer-reviewed yorunal would be good enough - but both would surely be the opposite of not disclosing
8h
comment How to create circles and or sections of a circle when the centre is inaccessible
@DacidButlerUofA Thanks for adding an illustration.
8h
comment For $f, g \in C^1$, $fg' - f'g \neq 0$ implies that the zeros interlace
Considering both questions is also a hint for the first part, as for each $x_0$, at least one of the quotients is defined and has nonzero derivative in a suitable open neighbourhood of $x_0$.
9h
comment Is the zero of a field irreducible?
As @MichaelAlbanese said, the usual variant of Def1 includes the condition that $a$ be non-zero. A related confusion may occur with prime in place of irreducible: We speak of a prime element only if it is nonzero, but the zero ideal is counted as prime ideal.
9h
revised Intersection of an Infinite Indexed Family of Sets
added 1 character in body
9h
answered Why isn't the Cantor Set contradictory?
9h
comment Homomorphism from a commutative group?
Could it be that $f$ is onto?
9h
answered Intersection of an Infinite Indexed Family of Sets
10h
comment Subgroup contained in all other subgroups
What prevents $H$ in th elast paragraph from being the trivial subgroup?
17h
answered Divide-and-conquer on a rectilinear polygon
21h
comment If $C$ is finite, closed, irreducible, we know that every such state $C$ is recurrent. What is a counter example of if $C$ isn't closed?
What is $C$ in the first place?
21h
answered How to create circles and or sections of a circle when the centre is inaccessible
21h
comment A question on function notation
@MarianoSuárez-Alvarez ... especially in the full form $f\colon \mathbb R\to\mathbb R, x\mapsto x^2$. The most important thing to notice is that one should never write "Let $f(x)$ be a function ..." because $f$ and not $f(x)$ is the function. The "$\mapsto$" is often a good way to avoid this bad style.
1d
reviewed Leave Open Fixed point equivalence
1d
answered What is the sum that the square root button on calculator does so I can do it without the calculator button
1d
comment Banach Tarski paradox in Minkowski space
Yes. Just decompose a threedimensional cross-section and "spread" the result.
1d
comment Totient Function $\varphi{(x)}=24$
@Lalaloopsy Well, an odd prime contributes at least a factor of $2$, hence $\phi(n)=24$ implies that $n$ cannot have more than three odd prime divisors; this doesn't help much here, though