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5h
comment A proof of a known identity using Fourier series
Well, how is this sum over $n=-\infty..\infty$ defined exactly?
5h
comment A proof of a known identity using Fourier series
Well, yes, that's a good observation. Nevertheless, it rather says that interpreting the desired formula $\sum_{n=-\infty}^{\infty}\frac1{n+a}$ is not straightforward (if possible in any way).
5h
answered A proof of a known identity using Fourier series
9h
comment Representation of $(\mathbb{Z}_{\frac{*}{5}},_{\times5})$ using Cayley table
Yes, that's correct, supposed you mean the 'multiplicative group of integers modulo $5$'. Also observe that $3=-2$ and $4=-1$ here, which explains the symmetry you got.
1d
comment How can the axiom of choice be called “axiom” if it is false in Cohen's model?
It simply means that $ZF$ implies neither $C$ nor $\lnot C$.
1d
comment Direct limite commute with Direct sum
Do we know something like 'the ideals $I_i$ are disjoint to all $J_j$'?
1d
comment If two monoids have equivalent action categories, are they isomorphic?
Considering the monoids $G$ and $H$ as categories, they will be Morita equivalent iff their idempotent completions are equivalent.
Jul
23
revised Quadratic form as generalized distance?
added 8 characters in body
Jul
23
revised How does one find the image of a linear transformation, given that T is a rotation followed by a projection?
added 2 characters in body
Jul
23
answered Quadratic form as generalized distance?
Jul
23
comment probability question of a set of features
Note that $P(A|B)=\displaystyle\frac{P(A\cap B)}{P(B)}$ supposed $P(B)>0$.
Jul
23
comment probability question of a set of features
Yes, @ana, that was my first thought too about this presentation of the problem. However, see Conrado Costa's answer. Observe that, as events, you listed all subsets of $\{a,b,c,d\}$.
Jul
21
comment Unorthodox definition of semi-abelian category
Semi-abelian categories according to nLab (e.g. the category of groups) don't have to be enriched over $\bf Ab$.
Jul
19
answered How does one find the image of a linear transformation, given that T is a rotation followed by a projection?
Jul
19
comment How can I compute the infimum of the following non linear functional
As the integral of an arbitrary function can be arbitrarily big in any very small interval, I would guess, the infimum would be the same ($-\frac25$), as we can approach $x^2$ by functions from $\mathcal M$, corrigating in smaller and smaller intervals...
Jul
19
comment How do the rows of a change of basis matrix form a basis for expressing columns?
Did you read on? Tries to explain it.
Jul
19
comment Inquiry about My Self-Study Plan for Real Analysis (associated with my undergraduate research)
I personally like that plan. But it might be 'safer' if someone would guide you (perhaps MathSE:)
Jul
18
comment Is the concept of a Universal Set an example of Russell's paradox?
As far as we don't have other things but sets, yes: Let $U$ be the union of all sets and $V$ be the set of all sets. If $x$ is a set, then so is $\{x\}$, and hence $x\in\{x\}\subseteq U$. On the other hand, if $x\in U$, then $x$ is an element of a set, hence is a set by initial hypothesis, so $x\in V$.
Jul
18
comment Fibonacci $\equiv -1 \mod p^2$
How you prove for a prime $3<p<1000$ that there is no such $n$?
Jul
18
comment Monotone map on a Preset
That's the 'structure preserving mapping' between preordered sets (or posets).