KalEl
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 Mar 8 answered Burnside's Lemma on regular octagon Dec 30 comment Determining the basis of a span of vectors for all values of $a$. $(a, 1, 1)$ and $(1,a,1)$ are the basis of what they span. (They are linearly independent and they span the vectorspace.) Do you want an orthonormal basis of something? Dec 30 revised Is it possible to find $\angle BOA$? added 112 characters in body Dec 30 answered Is it possible to find $\angle BOA$? Dec 30 revised Proving the limit Corrected, it should be $O(1/x^2)$ and not $O(x^2)$. Dec 28 comment What if the intermediate point is $c=(0,0)$ in the MVT? Right - I missed that. But in that case we know the $\nabla f(0,0)$ has to be the only value that can maintain continuity of $\nabla f$ around the origin, i.e. it has to be $(0, 1)$. Dec 28 answered What if the intermediate point is $c=(0,0)$ in the MVT? Dec 28 answered Finding $f(x)$ such that $\int_{a}^{b}f(x)dx=\sum_{k=a}^{b}f(k)$ Dec 28 comment Sum of $\sum\frac{1}{i^{i}}$ Edit: OP is interested in $\sum_{k=1}^\infty k^{-k}$. Dec 28 answered Proving the limit Dec 28 revised Let $a > 1$ be a real number and $n > 1$ be a positive integer. Prove that $a^n-1 > n\left(a^{\frac{n+1}{2}}-a^{\frac{n-1}{2}}\right)$. deleted 82 characters in body Dec 28 comment Let $a > 1$ be a real number and $n > 1$ be a positive integer. Prove that $a^n-1 > n\left(a^{\frac{n+1}{2}}-a^{\frac{n-1}{2}}\right)$. You're right. Edited. Dec 28 answered Let $a > 1$ be a real number and $n > 1$ be a positive integer. Prove that $a^n-1 > n\left(a^{\frac{n+1}{2}}-a^{\frac{n-1}{2}}\right)$. Dec 28 comment How can I count solutions to $x_1 + \ldots + x_n = N$? Agreed. The WLOG needs to be explained more... though this might be in a right direction. Dec 28 comment Find if two multi-dimensional parallelograms intersect Yes that's exactly how I did it, used a LP solver. Notice this problem is simpler than a full LP, since all I am interested in is if the feasible region is non-empty. Also there are some nice symmetries. I was wondering if there is any direct way to solve this problem. Dec 28 accepted Find if two multi-dimensional parallelograms intersect Dec 23 awarded Tumbleweed Dec 16 asked Find if two multi-dimensional parallelograms intersect Sep 9 awarded Stellar Question Aug 18 awarded Yearling