Hagen von Eitzen
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 Apr17 answered Why does the result follow? Apr17 comment Insights in solving systems of eqn? The for the moment forget about $I_3AI_4$, whatever that is. Try to obtain new - simpler - equations by adding / subtracting known equations. For example, add the first and third to immediately see what $x_3$ must be ... Apr17 answered If $xy=x^{-1}y^{-1}$, does this imply $x=x^{-1}$ Apr17 comment Dual Vector Space embedding In the first line you ask for an embedding, in the last line for a natural embedding. These are different questions (and have different answers). Apr17 comment Logarithm of a negative number Nothing. You dropped the condition "whenever $a,b>0$" from the full steatement of the identity. Apr17 answered Continuity of 1/x Apr17 comment When do eigenvectors converge? If $\{v_n\}_{n\in\mathbb N}$ is a sequence such that $A_nv_n=\lambda v_n$, it is not necessarily the case that $v_n$ converges in the first place. Think of $A=A_n=I$, $\lambda=\lambda_n=1$ for all $n$ and $v_n$ some "random" sequence. Apr17 comment Every integer greater than 1 is divisible by at least one prime. Can anyone please express this in logical notation Do you have predicates for "is integer", "is greater than", "divides", "is prime" and a constant symbol for "1" available? Apr17 answered Exercises in combinatorics Apr17 comment Exercises in combinatorics Where do cycles come from in 3)? Apr17 comment Irrationality of $\pi$ and circumference to diameter ratio. Note that $\frac13$ also has "never ending numbers after decimal". This doesn't contradict the fact that $\frac13$ is finite. Apr17 answered Explain “There is a unique function from $\emptyset$ to any set $A$”. Apr17 answered How would Intermediate Value Theorem be used in this question? Apr17 revised How would Intermediate Value Theorem be used in this question? added 8 characters in body Apr16 comment exercise involving exactness I assume here monomorphism only means left-cancelable? Apr16 answered Regular Expressions Help Apr16 comment Application of computers in higher mathematics Actually, a mathematican would often rather observe some interesting properties and from them go back to look for suitable axioms :) Apr16 comment If $a^2+b^2=1$ where $a,b>0$ then find the minimum value of $(a+b+{1\over{ab}})$ Well stat looks a lot like caclulus Apr16 comment cardinality with finite sets You do use transitivity, but to conclude $A\subseteq C$. Apr16 comment A question about entire function. There is an even more elementary solution, not to say trivial ... Btw., how do you find entire functions with poles?