Stefan
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 Mar 17 revised Relation between vertices and edges in a tree? added 10 characters in body Mar 17 comment Relation between vertices and edges in a tree? And less than $n-1$ edges is not possible if you require the graph to be connected Jan 13 comment Matrix multipication If $\omega^4 \neq 1$ we get $1 = b\omega^3 = \omega \omega^3 = \omega^4$, a contradiction. So if $\omega^4 \neq 1$ there are no solutions. Jan 13 comment Matrix multipication What do you get when you plug those values back in? Remember, $\omega^4$ is $1$, otherwise there are no solutions Jan 13 comment Matrix multipication Can't you just compare the entries in the first and last matrix? Then $a=1$, $b=\omega$, $c=\omega^2$ and $d=\omega^3$, leaving us with $1=\omega^4 = \omega^8 = \omega^{12}$ (from the last row). So $\omega$ has to be a fourth root of unity. Dec 1 reviewed Approve Limit of function, when $x$ approaches $a$ Dec 1 comment Limit of function, when $x$ approaches $a$ Well as you already said, the limit is equal to the derivate of $\ln(x)$ at the point $a$. You know that the derivate is $\frac 1 x$, so the limit is equal to $\frac 1 a$. Dec 1 reviewed Approve Evaluating $\int_0^2 x(8-x^3)^{\frac{1}{3}}\ dx$ Jul 20 awarded Yearling Jun 6 reviewed Approve Solution of an equation and a system of inequalities May 14 reviewed Approve substraction of groups in direct sum May 12 comment Question about principle ideals and polynomials and quotient ring construction? You are taking the ideal  in $R[X]$, thus $= \{ p\in R[X] | p = gf, g \in R[X]\}$. So it is every possible polynomial multiple of $x^2+1$. May 12 answered A complex variable function integrated over an infinitesimal disk May 10 reviewed Approve Evaluating the Legendre symbol $\left(\frac{5}{p}\right)$ using Gauss's lemma instead of quadratic reciprocity. May 10 reviewed Approve How do you take the derivative of a variable with respect to a different variable: May 10 reviewed Approve Probability of having k defined elements while choosing m elements from a set of N May 10 reviewed Approve A curious compactness confusion: space filling curves in the hilbert cube that contradict a bona fide theorem? May 10 reviewed Approve Complex numbers equivalence proof May 9 reviewed Approve Topology: Example of a compact set but its closure not compact May 8 reviewed Reject Calculating normalization constant in circle detection process