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 Yearling
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Feb
4
comment Intersection of connected open sets with union $[0,1]^2$ is connected
Do you mean that $U$ and $V$ are open in $[0,1]^2$?
Feb
2
reviewed Approve Is $(0,0)$ is a singular point of $x=0$
Jan
9
revised A pathological example of a differentiable function whose derivative is not integrable
added 2 characters in body
Jan
9
comment How to show $\phantom{d}_d C_0+\phantom{d}_d C_4 + \cdots = 2^{d-2} + 2^{\frac{d}{2}-1} \cos(\frac{d \pi}{4}) $?
I think that these equalities can be proved using series multisection.
Jan
5
answered Closed Subset of Connected Space with Boundary a Single Point is Connected
Dec
18
revised Differentiability for function $f(x) =$ greatest lower bound of $|x-\frac 1n|$ at $x=0$.
deleted 39 characters in body; edited tags
Dec
18
reviewed Edit Minimizing a quadratic function with constraints on some variables
Dec
18
revised Minimizing a quadratic function with constraints on some variables
Equation editing
Dec
15
comment Is there a direct proof that a compact unit ball implies automatic continuity?
@EricWofsey You are right, sorry.
Dec
15
comment Is there a direct proof that a compact unit ball implies automatic continuity?
Probably I am missing something, but I think that the proof that linear functionals defined on finite-dimensional spaces are continuous works in this case, namely: if $f:X\to\mathbb C$ is a linear functional then $\max_{\|v\|=1}f(v)$ exists, say $C$, so for any $w\ne0$ in $X$ we have $f\bigl(w/\|w\|\bigr)\leq C$, and thus $f(w)\leq C\|w\|$.
Dec
12
awarded  Yearling
Dec
9
answered Suppose $ \lim \left( a_{n}+a_{n+1} \right)=0 $. Show that $ \lim a_{n}=0 $ or $ 0 < \limsup a_{n} $.
Dec
9
comment Finitely generated torsion module over a Dedekind domain
This is my try (some/both steps may be wrong): We have $M\cong\oplus_i M_{P_i}$, and $\oplus_i M_{P_i}\cong S^{-1}M$ by definition of $S$.
Dec
3
reviewed Reject Determine if a point lies on a plane given an equation in standard form
Dec
3
reviewed Approve How to subtract two equations?
Dec
3
comment When does non-spanning imply linear independence in a free $R$-module
@leibnewtz For any ring $R$ we have that $\{a\}$ is $R$-linearly independent iff $a$ is a nonzerodivisor; on the other hand any two elements $a,b\in R$ are automatically $R$-linearly dependent ($(-b)a+ab=0$).
Dec
2
comment How to divide $C_n^k$ combinations into $C_n^k\times k/n$ distinct groups if $n/k$ is an integer?
Nice question! I will think about it.
Dec
1
revised Explicit formula for Bernoulli numbers by using only the recurrence relation
added 30 characters in body
Dec
1
revised Obtaining binomial coefficients without “counting subsets” argument
added 60 characters in body
Dec
1
revised Divisibility of polynomials in a subfield of a field.
added 122 characters in body