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location Cleveland Heights, OH
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seen Jan 2 at 12:05

Professor emeritus at Cleveland State University. I’m a set-theoretic and general topologist with an interest in combinatorics. I’m also interested in linguistics, especially historical linguistics.


May
27
awarded  Nice Answer
May
27
comment Differentiate $g(t)= {e^t - e^{-t} \over e^t + e^{-t}}$
@Mariana: I did wonder if that was the case, but sometimes books or teachers do ask questions like that. No harm done!
May
27
revised Differentiate $g(t)= {e^t - e^{-t} \over e^t + e^{-t}}$
added 547 characters in body
May
27
answered Differentiate $g(t)= {e^t - e^{-t} \over e^t + e^{-t}}$
May
27
revised Solving summation $2n+2^2(n-1)+2^3(n-2)+…+2^n$
added 493 characters in body
May
27
answered Solving summation $2n+2^2(n-1)+2^3(n-2)+…+2^n$
May
26
revised Partition Properties
Added link.
May
26
comment Interesting Normality Condition (topology)
@Eric: No, the chimney analogy is very physical: one way to climb a rock chimney (or a house chimney, if it’s big enough) is to brace your feet against one side and your shoulders against the other. Then you step up with your feet (building $G_{n+1}$ from $G_n$) and then use your hands behind you to slide your shoulders up the same amount (building $H_{n+1}$).
May
26
answered Prove if $n^2$ is even, then $n$ is even.
May
26
revised Interesting Normality Condition (topology)
added 372 characters in body
May
26
answered Interesting Normality Condition (topology)
May
26
comment Interesting Normality Condition (topology)
Did you want $A\cap\operatorname{cl}V_i$ to be empty, rather than $A\cap V_i$?
May
26
answered Partition Properties
May
26
comment Delta System Lemma: Kunen’s proof.
@Vinicius: You’re very welcome!
May
26
comment Delta System Lemma: Kunen’s proof.
@Vinicius: Yes, that’s right. In general $[X]^\kappa$ is the family of subsets of $X$ of cardinality $\kappa$, and $[X]^{<\kappa}$ and $[X]^{\le\kappa}$ are then defined as you would expect.
May
26
answered A question on countability of isolated points of a subset of R
May
26
answered Delta System Lemma: Kunen’s proof.
May
26
comment elements of sets, subsets relations
@Heidi: It does make it easy, doesn’t it? :-) You’re welcome!
May
26
revised Why do we believe the Church-Turing Thesis?
A significant typo, LaTeX.
May
26
comment Ties in Matching Pennies
@pad: You’re welcome.