106,630 reputation
696194
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 1 year, 11 months
seen 7 mins ago

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


Jul
28
answered Tangent line at $x_1$ to polynomial curve $p(x)$ of degree at least $2$ implies $x_1$ is a double root of $p(x) - p^{'}(x_1)(x-x_1)$?
Jul
25
comment RSA encryption. Breaking 2048 keys with index
In other words, the key to breaking the randomly generated keys is to convince people to use your specialized random number generator :)
Jul
23
comment Paradoxical Game Show Problem
As soon as you impose a probability distribution on the money amounts, the paradox gets resolved (because when seeing an unusually high amount in your chosen box, the probability that yours is the smaller amount decreases)
Jul
23
revised finding a group that satisfy: $x,y\in A_n\Rightarrow x\in y \vee y\in x \vee y=x$
edited tags
Jul
23
comment finding a group that satisfy: $x,y\in A_n\Rightarrow x\in y \vee y\in x \vee y=x$
What about the set $n$ itself?
Jul
23
answered Equivalence Graphs
Jul
23
comment My proof of the recursion principle (without the axiom of replacement)
I'm not very happy with "maximum element of domain". Why not use replacement to take the domain of $f$ itself? (This may require some special cases near $0$) Or do you already have $n^-$ on $\mathbb N\setminus\{0\}$ readily available?
Jul
23
comment Calculate distance between two objects based on their visible height for a specific focal length
A focal length of 35mm means that a point at infinity is mapped to a point 35mm behind the lens. However if your 15cm object is mapped to an image of 12cm, i.e. almost its original size, we are talking about the lens moved considerably away from the image plane (namely approximately into the middle between image plane and object; we'd have exactly the middle if the image size were equal to the object size). At any rate, without additional information, only the relative distances of the objects from the lens can be inferred from the quotient of their sizes.
Jul
23
comment Prove that intersection of connected spaces is connceted.
Let $A$ be the unit circle and $B$ the $x$-axis within the two-dimensional plane. Which of $A,B,A\cap B$ are conncted?
Jul
23
comment Why does this graph only the positive side
Hint: Do you think that $\sqrt[4]{x^2}=x^{2/4}=x^{1/2}=\sqrt x$ for all real numbers $x$?
Jul
23
answered Question concerning how a map extends to a homomorphism.
Jul
22
comment Where's the problem with a false “proof”: $\;1^0 = 1^2 \overset{?}\implies 0 = 2$
Apparently it is. Otherwise, we'd have $0=2$.
Jul
22
comment Does the boundaries of non-disjoint sets in Euclidean space have common element?
Well, you need to add a few conditions. For example if the sets are open, not disjoint, not contained in one another, and connected ...
Jul
22
comment Primitive-recursive functions and polynomial equations
Unless $K(m,n)$ is constant, $\prod_{i=0}^{K(n,m)}(P(n,m,i)-Q(n,m,i))$ is not of the form $P(n,m)-Q(n,m)=0$.
Jul
22
answered Primitive-recursive functions and polynomial equations
Jul
22
comment Proving some properties of $\Bbb N$ without using recursion
@Graduate I don't think that William wanted to object against referencing the axioms, but against referencing them by a local obscure notation. Saying Axiom of Infinity or simply INF instead of ZF7, Axiom of Power Set or simply POW instead of ZF4, Axiom Schema of Separation or simply SEP instead of ZF5 would have made a reference to the axioms as intended - and the reader would know which are meant.
Jul
22
answered Proving some properties of $\Bbb N$ without using recursion
Jul
22
answered An isomorphism question
Jul
22
answered About the subspace of polynomial vector space
Jul
22
answered May a monoid have two disjoint submonoids?