106,269 reputation
696194
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 1 year, 10 months
seen 20 hours ago

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


Sep
9
comment How can I demonstrate that the decimal equivalent for a binary number consisting of $n$ $1$'s is $2^n-1$?
It's nozt the decimal equivalent, it's simply the number
Sep
9
comment Is it appropriate to use conjectures in contest?
That would have been my conjecture as well
Sep
9
comment In a tree, is there always a sink where every longest path ends in?
@BobWhiz You'd have 1-4-6 and 2-4-5 as paths of maximal length, hence no candidate for a "sink".
Sep
9
answered A few questions about “small” transitive sets.
Sep
9
revised Evaluate the integral $\int_{r\leq R}\frac{\mathrm dr}{r^2-k^2}$
title not just math and not dispaystyle
Sep
9
answered Notation of Set without arg max element?
Sep
9
comment Subtraction two points on elliptic curve.
Yes, the elliptic curve is a group and $Q$ has an inverse
Sep
9
answered Why do these expressions tend to zero?
Sep
9
comment What is the difference between a Definition and a Theorem?
@MarcvanLeeuwen Yes, but I wanted to stick with the rectangle scenario. Of course, merely linguistic considerations drive us to use property (i) as "the" definition of rectangle.
Sep
9
comment Unsolved problems in number theory
Indeed, this definitely matches the OPs demand that an 18 year old can understand the problem. Easy understandability of partial solutions, recent progress etc. was not asked for.
Sep
9
answered Continue a Sequence
Sep
9
reviewed Approve suggested edit on Proving Inequality with Square Roots and Algebraic Manipulation
Sep
9
comment Triangle divided into equal halves
Second hint: How do the areas of similar triangle relate, if you know the scaling factor?
Sep
9
answered What is the difference between a Definition and a Theorem?
Sep
9
answered Is there an example that proves $( \exists x)(P(x) \land Q(x))$ is not equivalent to $( \exists x)P(x) \land ( \exists x)Q(x)$
Sep
9
answered Does the formula $(x^n)' = nx^{n-1}$ fail for some value of $n \in \mathbb{Z}$?
Sep
9
comment There exists a countable set of mutually orthogonal trigonometric functions which form a basis for $L^2(T)$. Proof?
Not every countable set of mutually orthogonal trigonometrix functions forms a basis for square integrable fucntion space. And in fact I doubt countable for the general case.
Sep
9
answered Intuition behind proofs by rules of inference
Sep
9
answered How many sylow $3$-subgroups of $A_4$ are there?
Sep
9
comment What is the max of $n$ such that $\sum_{i=1}^n\frac{1}{a_i}=1$ where $2\le a_1\lt a_2\lt\cdots\lt a_n\le 99$?
@mathlove The answer to "Is this the max?" is "No"