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Dec
7
awarded  Popular Question
Dec
2
awarded  Yearling
Jul
2
awarded  Curious
Oct
5
accepted How to iterate over power set in MAGMA?
Oct
5
revised How to iterate over power set in MAGMA?
added 141 characters in body
Oct
5
asked How to iterate over power set in MAGMA?
Sep
11
accepted Picking out columns from a matrix using MAGMA
Sep
9
asked Picking out columns from a matrix using MAGMA
May
23
revised Extending an ideal of a polynomial ring to a polynomial ring with more indeterminates. Is it a tensor product?
deleted 85 characters in body
May
16
accepted Is the image of a tensor product equal to the tensor product of the images?
May
16
comment Is the image of a tensor product equal to the tensor product of the images?
Thanks a lot for great answer. I don't quite see what the unique injection $\mathbb{Z}/2\mathbb{Z}\rightarrow\mathbb{Q}/\mathbb{Z}$ is though...could you please tell me? And what if all the modules $A,A',B,B'$ are free $S$- modules (even finitely generated), do we then have $$\operatorname{im}(\phi\otimes\psi)=\operatorname{im}(\phi)\otimes_{S}\operator‌​name{im}(\psi)?$$
May
16
asked Is the image of a tensor product equal to the tensor product of the images?
May
5
comment Showing that the Taylor series of $f(x)=\frac{1}{\sqrt{1+x}}$ converges to $f$ on (I think) the interval (-1,1].
Well, thanks a lot. This is a first year calculus exercise though, and neither complex analysis nor binomial coefficients involving non-natural numbers are part of the curriculum...far from it:)
May
5
asked Showing that the Taylor series of $f(x)=\frac{1}{\sqrt{1+x}}$ converges to $f$ on (I think) the interval (-1,1].
May
5
accepted Manipulation of some power series (probably integration or derivation).
May
4
comment Manipulation of some power series (probably integration or derivation).
Well, but using the series for $ln(1+x)$ and $ln(1-x)$ together with $\ln(a/b)=\ln(a)-\ln(b)$, which I had already tried, doesn't yield the deisred identity. I am pretty sure one is supposed to use the sum for $\frac{1}{1-x^2}$ mentioned above. And the absolute values, pointless though they are, I think may be a hint that one is supposed to integrate both sides of something, since \integral 1/y = ln|y| + C. But I still have no idea how to solve this exercise.
May
4
asked What happens to the sequence $a_n=\frac{3\cdot5\cdot7\cdot\ldots\cdot(2n-1)}{2\cdot4\cdot6\cdot\ldots\cdot2n}$ as $n$ tends to $\infty$?
May
3
asked Manipulation of some power series (probably integration or derivation).
Apr
28
awarded  Commentator
Apr
28
comment When is every spanning tree of a connected graph the union of spanning trees of its subgraphs?
In general, if the proposition holds for some $\{H_i\}$, then it holds for any "coarser partition" of $\{H_i\}$ as well.