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Apr
7
answered An equivalence of AC
Apr
7
comment Are there non-surjective homeomorphisms?
In other words, only itself should be in vold. Or you might ask, why homeomorphims of a space ...? Aren't all homeomorphisms defined on a space?
Apr
7
comment Definition of groups in a more abstract way
Regarding 1, whhat do you mean with $e(1)$? This need not be a concrete category.
Apr
7
comment Definition of groups in a more abstract way
Regarding 3, existence of two-factor products is the same as existence of finite products. $G_1\times \ldots \times G_n\cong (\ldots(G_1\times G_2)\times \ldots )\times G_n$ canonically. (The diagrams already use three-factor product $(G\times G)\times G$, in the form of repeated two-factor products, and the canonical isomorphism with $G\times(G\times G)$).
Apr
7
answered Inductions and proofs
Apr
6
answered if g'(x) tends to 0 as x tends to infinity, how to prove g(x)/x tends to 0 as well
Apr
6
comment Are mini-Mandelbrots known to be found in any fractals other than the Mandelbrot set itself?
Depends a bit on what you accept as mini-Mandelbrot (you know even those "copies" of $M$ in $M$ itself are not exactly copies ...)
Apr
6
comment Show that an integral can be made as small as possible.
Pick $\delta$ such that $\int_\delta^1\frac{\mu(s)}{s}\,\mathrm ds$ differes from $\int_0^1\frac{\mu(s)}{s}\,\mathrm ds$ by less than $\epsilon$?
Apr
6
answered Groups - identity - abstract algebra
Apr
6
comment Is every set a pointed set?
If $A$ is a (nonempty) set, then $A$ is not a pointed set. However, if $a\in A$, then $\langle A,a\rangle$ is a pointed set. So there is little sense (not to say: no point) in talking about a set being pointed or not before you pick a point.
Apr
6
answered Question about open and closed sets
Apr
6
answered Proving that if $E, F$ are equivalence relations on $A$ and $E \subseteq F$, then there is a surjection from $A\setminus E$ to $A\setminus F$
Apr
6
answered How can i solve limit.
Apr
5
comment arc length on circle
It should read $[t,t+dt]$.
Apr
5
awarded  Great Answer
Apr
5
comment What modular arithmetic theorem is being ignored here?
No theorem is ignored, but there is a "non sequitur" in 1.
Apr
5
answered What modular arithmetic theorem is being ignored here?
Apr
5
comment A property of integers
Did you try $a_0=81$? ;)
Apr
5
comment Interpretation of Riemann rearrangement theorem
My gut feeling is that Nature does know how to add such things usually: E.g. in a lattice sum ordered by distance from the point of interest. At least this corresponds to the fact that in finite objects the infinite sum is only an approximation that ignores all far away points. And even in a truely infinite case, the finite age of the Universe does not allow any influence from too far away points ...
Apr
5
answered Are these subgroups of G only subgroups if G is abelian?