28,886 reputation
1938
bio website jungenschaft-hohenstaufen.de
location Berlin, Germany
age 33
visits member for 2 years, 7 months
seen Mar 31 at 9:56

Jan
10
answered Help with understanding this linear functionals argument
Jan
10
comment If $AB=-I_n$, then prove that $det(I_n+BA)=2^n$
We have $$ I + BA = B(B^{-1} + A) = B(I + AB)B^{-1},$$ that is $I + BA = 0$ under the given hypotheses.
Jan
9
revised strictly convex function when plotted but second derivative not unambiguously positve
added 41 characters in body
Jan
9
comment A question on Cauchy sequence in topological abelian group
@MartinBrandenburg Thx. Done.
Jan
9
revised A question on Cauchy sequence in topological abelian group
edited body
Jan
9
answered Proving this limit: $\lim\limits_{n\to\infty}\sqrt [n]n=1$
Jan
9
answered A question on Cauchy sequence in topological abelian group
Jan
8
comment Prove that the set of one-to-one function $f: S\to S$ is a group with composition as group operation.
The one-to-one functions do not form a group. The one-to-one and onto functions do.
Jan
8
reviewed Close Evaluating a series with some given formula
Jan
8
revised Let A be a set in the Euclidean space. Is the set A relative open with respect to its closure?
added 323 characters in body
Jan
8
answered Let A be a set in the Euclidean space. Is the set A relative open with respect to its closure?
Jan
3
comment Product of positive matrices
$xx^T \ne x^Tx = \|x\|^2$.
Dec
26
reviewed Approve suggested edit on Direct proof: $\sqrt{13}$ is irrational
Dec
21
answered Probability Differentiation
Dec
20
revised Let V be an inner product space. If $ x⊥y $, then show that
TeXification
Dec
20
reviewed Leave Open What underlies formal logic (or math, generally)?
Dec
20
reviewed Close How many terms do I need to estimate $\sum_{i=1}^\infty 1/n^4$?
Dec
19
answered Function of a set of r.v.'s measurable w.r.t. the $\sigma$-algebra generated by the r.v.'s
Dec
19
reviewed Leave Open If $a|(b-c)$ does it follow that $a|(b+c)$?
Dec
19
reviewed No Action Needed Probability of two rolling dice