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

Dec
13
revised Find the series expansion of $f(z)=\frac{4}{(z-1)(z+3)}$ around $z_0=-1$.
fixed title
Dec
13
answered How to calculate a matrix with its orthogonal complement known?
Dec
12
revised Prove the following trigonometric identity.
TeXification
Dec
12
reviewed Approve suggested edit on Prove the following trigonometric identity.
Dec
12
revised boundary conditions after change of variables
TeXification
Dec
12
comment Is there an Artinian ring with exactly two prime ideals which their product is non-zero?
Thanks ... it was to easy ...
Dec
11
comment Improper Multivariable Integrals
No, it represents (if you want to say it like that) $n-1$ 1-dimensional integrals, as a sphere is a $n-1$-dimensional object. I wanted to mark that we integrate with respect to the surface measure of the sphere.
Dec
11
comment Prove or disprove matrix $A$ and $A^T$ is Matrix congruence?
$A$ and $A^t$ are similar: math.stackexchange.com/questions/62497/…
Dec
11
comment Radius of convergence of a power series.
Note that your attempt only shows that $\limsup a_n^{1/n} \le 1$, that is $R \ge 1$. To prove that $R=1$ you have to prove that also $\limsup a_n^{1/n} \ge 1$, that is find a sequence of $n$s with $a_n^{1/n} \to 1$
Dec
11
comment matrix method for solving system of linear equations
@MarcvanLeeuwen Thanks ...
Dec
11
answered Entropy Solution of the Burger's Equation
Dec
10
comment maximal subgroup of a group
$M$ being maximal only gives you $N_G(M) = M$ or $N_G(M) = G$.
Dec
10
comment Improper Multivariable Integrals
(1) Yes, $rS^{n-1} = \{rx \mid x \in S^{n-1}$. And by writing $dS(x)$ I tried to make explicit that the variable with respect to which we integrate is $x$.
Dec
10
reviewed Approve suggested edit on There exists $c\in [a,b]$ such that $\int_a^c f(t)dt = \int_c^b f(t)dt$
Dec
10
answered Derivative of function that includes norm
Dec
10
comment Improper Multivariable Integrals
Note that $\{x \in \mathbb R^n \mid \left| x\right| \ge 1\} = \biguplus_{r \ge 1} rS^{n-1}$, where $S^{n-1}$ denotes the unit sphere, i. e. the set of vectors with unit length.
Dec
10
reviewed No Action Needed Is $ x \log x = O(x^{1+\epsilon})$ for every $\epsilon > 0$?
Dec
10
reviewed No Action Needed Prove $ \mathrm{E}\left[\max_{1≤i≤\infty}|S_i|\right]≤2\sqrt{b} $?
Dec
10
reviewed Leave Open Use induction to prove a congruence relation
Dec
10
reviewed Leave Open Poems related to mathematics