4,428 reputation
1723
bio website
location
age
visits member for 2 years, 2 months
seen 7 hours ago

I'm a student of mathematics in Germany.


Dec
14
accepted Are the polynomial functions on $S^1$ dense in $C(S^1,ℂ)$?
Dec
14
accepted Can $ℂ$ be viewed as a (nontrivial) field of fractions?
Nov
29
accepted Why is every category in which all (even large) limits and colimits exist thin?
Nov
6
accepted Is a set open in a product of spaces if all its segments are open in their factors?
Oct
27
accepted Does $f ≥ g$ always imply $f^{-1} ≤ g^{-1}$ for invertible $f, g$?
Sep
23
accepted Example of a convex set whose closure is not convex?
May
20
accepted Embeddings $A → B → A$, but $A \not\cong B$?
Apr
10
accepted How could I have found the closed form of $\sum_{k=1}^n \frac{k}{(k+1)!}$ in advance?
Mar
18
accepted Is every left maximal ideal the annihilator of a simple left module?
May
28
accepted Taylor expansion of $(1+x)^α$ to binomial series – why does the remainder term converge?
May
1
accepted Why is $\sum_{d \mid N} N/d ϕ(N/d) ϕ(d) = N^2 \prod_{p \mid N} (1 - 1/p^2)$?
Apr
28
accepted sine, cosine and the exponential by their differential equations
Jan
21
accepted Is there a sequence whose arithmetic means lie dense in $[-1..1]$?
Nov
24
accepted Does one restrict oneself when leaving out the inversion in the signature of groups?
Nov
17
accepted Is the inversion of an invertible map given by a formula again given by the inversion of that formula
Nov
15
accepted How to interpret material conditional and explain it to freshmen?
Nov
11
accepted troubles proving every subset of a finite set is finite with naive set theory
Nov
1
accepted is a non-falling rank of smooth maps an open condition?
Oct
20
accepted Complex projective line hausdorff as quotient space
Oct
10
accepted Visualizing Infinity discerning countable and uncountable