Matthew Pressland
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 Nov5 comment re-writing a mathematical expression @EmmaTebbs I agree this is a slightly difficult question to tag - myself and another user have now retagged it. Physics and matlab are both relevant to the context, and I also added algebra-precalc because it's essentially about manipulating expressions (although the expressions are a little more involved than those that would normally occur under this tag!). Nov5 revised re-writing a mathematical expression edited tags Nov5 comment re-writing a mathematical expression @EmmaTebbs They also use $f$ again in a second expression on the next page, so its more efficient to define it separately. (It also prevents the formula from $K_{\mathrm{int}}$ from breaking over three lines, which would make it harder to read.) Nov4 awarded Nice Answer Nov4 comment Can basis vectors have fractions? @Bill Since my point was that the operation of clearing denominators doesn't make sense in general, it didn't seem worth identifying the most general situation in which it does makes sense. Nov4 revised $f(x)=x^p-a$ is either ireducible or has a root? added 36 characters in body Nov4 comment $f(x)=x^p-a$ is either ireducible or has a root? Your first assertion is false; if $k=\mathbb{R}$ or $k=\mathbb{C}$, then $f$ is not irreducible for most values of $p$, by the fundamental theorem of algebra. Nov4 revised Can basis vectors have fractions? added 134 characters in body Nov4 answered Can basis vectors have fractions? Nov4 comment Can basis vectors have fractions? I don't think you said what you mean - if $v$ is a vector in some basis, then $cv$ is definitely not in the basis unless $c=1$! But you can replace $v$ by $cv$ and you will have another basis for the same space. Nov4 comment Towers of Hanoi Starting From Initial (Legal) Configuration? Your description should be close enough though, and I think makes the point clearly - the algorithm will move you from one corner of the triangle to another in a straight line, but your picture explicitly shows the $6$ (at least once you label the pegs) legal configurations that don't occur as a stage in the traditional recursive solution. (And if you increase the number of disks, more such arrangements exist). Nov4 answered What if not connectedness defines a graph? Nov4 comment Show that the map $T_U:W\to U^{*}$ is linear $\tau$ isn't the dot product - its arguments even come from two different spaces! It is just some bilinear map $W\times V\to\mathbb{K}$. It's not unusual to use the $U^\perp$ notation for orthogonality with respect to other bilinear forms than the dot product. Since you are given that $\tau$ is bilinear, the question is merely asking you to see that this implies the linearity of $T_U$ - this seems to me to be mainly an exercise in distinguishing linearity of $(T_U\mathbf{w})(\mathbf{u})$ in $\mathbf{w}$ from linearity in $\mathbf{u}$. Nov3 comment Eigenvectors of a Rotation Matrix Even banning the identity matrix isn't enough; the matrix $$\begin{pmatrix}-1&0&0\\0&-1&0\\0&0&1\end{pmatrix}$$ is also a rotation matrix admitting non-orthogonal eigenvectors. Nov3 comment Eigenvectors of a Rotation Matrix The assumption of the first question is false; any eigenvector of any matrix can be rescaled arbitrarily. Nov3 revised A leveling on a non-empty set $A$ is a function $d$ from $A \times A$ into $A$… added 108 characters in body Oct31 revised Show that the unit sphere with centre $0$ in $\mathbb{R}^d$ is compact. added 31 characters in body Oct31 reviewed Leave Open Negative index coefficients of Laurent series for 1/sin(z) Oct31 reviewed Leave Open Funny problem. How to average over periodic numbers Oct31 reviewed Edit Example of non fractional ideal