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1d
answered Find two matrices $A$ and $B$ such that matrix $AB$ that is invertible but $BA$ is not.
2d
comment Prove this result relating to the sign of a permutation
Do you know that sign is a homomorphism?
2d
comment Prove this result relating to the sign of a permutation
The $\forall $ makes little sense here
2d
answered Abelian group which is not one of these
2d
answered There exist a set $X$ such that the number of function $y: x\to \{1,2,3\}$ is $1000$.
2d
answered Intersection of elements of a union
2d
answered $Q=\{ 1,2,…n \}$. $S \subset Q$, let $p(S)$ be the product of elements of $S$, Find the sum of reciprocals $\frac{1}{p(S)}$ for all $S \subset Q$.
2d
comment Recurrence equation $f(g\cdot x)/f(x)=t$
@TomH "If I go $\ln g$ to the right, I go $\ln t$ up" really suggests a linear solution (until Henning Makholm comes along and adds his wiggly someting)
2d
revised Recurrence equation $f(g\cdot x)/f(x)=t$
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2d
answered If $\frac{n_k}{m_k} \rightarrow \xi \in \mathbb R \setminus \mathbb Q$ then $m_k \rightarrow \infty$
2d
answered linear map $f:V \rightarrow V$, which is injective but not surjective
2d
revised Recurrence equation $f(g\cdot x)/f(x)=t$
edited title
2d
answered Recurrence equation $f(g\cdot x)/f(x)=t$
2d
comment Is the intersection of a finite language and an infinite language always a regular language?
The intersection of finite and infinite is certainly finite, hence regular
2d
comment Is there any relation Trace and Boundary?
Not really, I suppose. We may interprete "trace" as meaning something like "footprint", in the the linked pdf th e"footprint" the function leaves on the boundary, and for matrices just meaning as much as "a characteristic property"
2d
comment Identification of a quadrilateral as a trapezoid, rectangle, or square
Question 75 before the OP question asks to name an angle and I wondered why $\langle DBC$ was not among the suggestions, which shows that there is not the angle frmed by the dashed rays ... Nevertheless, I would certainly fail Q71 :)
2d
comment Fields of arbitrary cardinality
Hm, but wouldn't multiplication be noncommutative here? I guess taking the polynomial ring with all elements of $X$ as variables, i.e. using maps $X\to\mathbb N_0$ with finite support in place of finite strings might be better.
2d
comment Fields of arbitrary cardinality
+1 for not being "choicy". - $f_0$ corresponds to the empty string, hence need not play a special role.
2d
answered If I know the order of every element in a group, do I know the group?
2d
revised Distances to the center of points uniformly distributed in a disk
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