286 reputation
17
bio website jstuber.net
location North Rhine-Westphalia, Germany
age 49
visits member for 3 years, 8 months
seen Apr 4 at 14:40

I'm a free-lance embedded software developer who likes computer science, mathematics, electronics and foreign languages.

e + 1 = 0

eπ√163 ≅ 6403203 + 744

rot13("fr") = "se"


Mar
9
comment Can numbers exist outside of the number space?
Ordinals and cardinals are extensions of natural numbers but not integers.
Jan
21
comment How do I convince my students that the choice of variable of integration is irrelevant?
In logic it is an axiom, so IMHO it is fine to use intuition to justify it. Note that you have to be careful not to capture other variables which are free inside the function or integral.
Aug
6
awarded  Nice Answer
Oct
23
comment Integral solutions of $x^2+y^2+1=z^2$
You are not trying to solve Project Euler problem 224, are you? projecteuler.net/problem=224
Oct
9
comment Why is it called a 'ring', why is it called a 'field'?
And it is still "Körper" in German.
Oct
3
comment How to derive a function to approximate $\sqrt{3}$?
It is much older than Newton's method: en.wikipedia.org/wiki/…
Sep
12
comment Mathematical operation with unique result
These are of course ordered pairs, edited to make that explicit.
Sep
12
revised Mathematical operation with unique result
added 8 characters in body
Sep
9
answered Mathematical operation with unique result
Sep
9
comment In set theory, how are real numbers represented as sets?
You have to exclude at least <0,0> in the construction of Q. It would be related to all other pairs so transitivity would fail.
Aug
31
comment What is the result of infinity minus infinity?
This infinity of a denumerable set of things is normally written ω (omega), it is the least infinite ordinal (there are many many more infinite ordinals).
Aug
26
comment Who invented $\vee$ and $\wedge$, $\forall$ and $\exists$?
They also had funny names as mnemoics for their inference rules, such as Barbara, Celarent, etc, where the vowels encoded the sentence forms.
Jul
28
awarded  Yearling
Jul
24
comment Real world applications of Pythagoras' Theorem
Please list what you already have.
Jul
20
comment divisibility of ABCD+DCBA by 11
For an odd number of digits the middle digit will lead to a summand 2 * d * 10^k, so it can only work for divisibility by multiples of 2 and/or 5.
Jul
14
answered Are all numbers real numbers?
Jul
14
comment Are all numbers real numbers?
The rationals don't have gaps, they are dense.
Jun
19
comment Finding the 10001th Prime
@Luboš Please delete your comment, it is a spoiler for those who still want to solve the problem.
Jun
18
answered Proof that cube has 24 rotational symmetries
Jun
17
comment How to build up the congruence equation?
(x+1) is to accommodate our human way of counting starting at 1.