Alex Becker
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40,372
99/100 score
 May15 awarded Nice Question May15 comment Calculating fundamental group and homology group to prove not homeomorphic to each other @MarianoSuárez-Alvarez Yes, thanks. May15 revised Calculating fundamental group and homology group to prove not homeomorphic to each other added 1 character in body May15 answered Calculating fundamental group and homology group to prove not homeomorphic to each other May15 comment Random nonegative solution of multivariate linear Diophantine equation Do you just need a solution, or do you need an algorithm which is equally likely to produce any of the solutions? May15 comment We can tell that f is not a translation or glide reflection (hence, it must be a rotation). How? Are we assuming that $f$ is an isometry? May15 comment Is this math valid? @MJD On the other hand, it is not unreasonable to assume the worst-case scenario in questions about regulation, esp. public health. May15 answered A matrix $M$ that commutes with any matrix is of the form $M=\alpha I$ May15 comment Is this math valid? I think the assumption is that the milk contains 100 micrograms per kilogram. Since two cups is about half of a kilogram, it would then contain about 50 micrograms. May14 comment Help with proving that the transpose of the product of any number of matrices is equal to the product of their transposes in reverse @1west Try using induction. We have $A^TB^TC^T=(BA)^TC^T=(C(BA))^T=(CBA)^T$. Proceed in the same manner. May14 comment Do circles exist $\pi$ is irrational, so its decimal expansion never ends, but that doesn't mean it doesn't exist. May14 comment Convergence of the series $\sum \frac{(-1)^{\sqrt{n}}}{n}.$ I'm a little confused. The real-analysis tag and $<$ sign seem to imply you're working in $\mathbb R$, but generally $(-21)^{\sqrt n}$ will not be real. May13 comment Find the volume of a cone whose length of its side is $R$ I have merged this question with your previous one. May13 comment True or False: $i^2 = -1$, $\mathbb{C} = \mathbb{R}^2$ @Optional I think this answers the part of your question that makes sense. If you understand this answer, then I can't understand what your remaining question is. May9 comment finite field extension and normality What definition of normality are you using? May9 comment can I show this set is closed? @DavidMitra I would go so far as to call this a duplicate of that question. Do you agree? May9 comment can I show this set is closed? No, you cannot. May9 comment The Category of Small Categories: a Zoo of Functors. Can you give an example of how it would be useful? May9 comment The Category of Small Categories: a Zoo of Functors. I didn't downvote, but I'm not really sure why one would want such a site. May9 comment Question with Isolated Points The idea is to find an interval around the isolated point which does not contain any other element of the set.