hardmath

Knoxville, TN

Age: 60

Enjoys programming in Prolog.

Richard O'Keefe: "Prolog is an efficient programming language because it is a very stupid theorem prover."

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4h	answered	Requests for Reopen Votes
17h	comment	Testing if two 12x12 matrices have the same determinant The notion that this condition has to be tested "for a trillion of matrices" suggests 1) that $Q$ is known apriori to have some special structure (otherwise the expectation that the condition holds at random is slight), and 2) that a better approach might be to characterize all matrices $Q$ with this property (with an efficiently checkable formulation).
2d	reviewed	Leave Open Find an equation for the tangent to the curve at the given point.
2d	reviewed	Close Books to understand the construction of all groups of a specific order
2d	comment	Matchings between 2 or more equal size sets Exponent in general case should be one less, `(m!)^(n-1)`, as consistent with the case of two sets.
2d	revised	Matchings between 2 or more equal size sets Improved wording
Jun 15	answered	what does v[2] means in terms of structure in c?
Jun 15	comment	Finding the area of $\int^1_{-1}\frac{1}{x}dx$ The title and the body of the question ask somewhat different things. The integral in the body is called an improper integral, because the limit of the integrand at one of the limits of integration is infinite or does not exist. In some cases an improper integral may be evaluated by taking a one-side limit approaching a singularity, but in this case it turns out the integral cannot be evaluated that way. Depending on the application the integral in the title might be treated more favorably, cancelling in some way the negative "area" to the left of the origin with positive area on the right.
Jun 15	reviewed	Approve suggested edit on Integrating $\exp (\exp (x))$
Jun 15	comment	Explanation of why $\frac{d}{dx} e^x=e^x$ possible duplicate of How do I prove that the exponential function $e^x$ has gradient $e^x$ from first principles?
Jun 14	revised	Number of solutions of a positive integral quadratic form is finite? fixed latex typo; edited body; added 3 characters in body
Jun 14	revised	Number of solutions of a positive integral quadratic form is finite? Added details for equivalence of coercivity with pos. defn. quadratic form.
Jun 14	comment	Number of solutions of a positive integral quadratic form is finite? Sure, I'll add more details.
Jun 14	comment	SQL select count case comparing 2 columns Start with something that works, e.g. just do a count() on the table. Your syntax above has errors, so it's a poor starting point. You have a `COUNT()` next to `CASE`, which doesn't make sense.
Jun 14	answered	Number of solutions of a positive integral quadratic form is finite?
Jun 14	comment	SQL select count case comparing 2 columns Treatment of Nulls is a valid concern, but I don't see anything in the Question that suggests how Nulls (if any) should be counted.
Jun 14	answered	SQL select count case comparing 2 columns
Jun 14	comment	Get full DOM stack as a string Please specify what programming context you want "the full DOM... as a string". Putting a javascript tag on the question doesn't much clarify what you're trying to do.
Jun 13	comment	Finding a concave function that minimize the middle value while the boundary values are fixed Title says "maximize the middle value" but text of Question asks to find $argmin_f f(1/2n,1/2n,\ldots,1/2n)$, i.e. a minimization. I'd guess you intend the latter (and that 1/2n means $(2n)^{-1}$), but it could stand clarification.
Jun 12	comment	Optimal strategy for covering all possible subsets A good resource for covering designs is the La Jolla Covering Repository maintained by Dan Gordon. A survey of constructions and bounds is here, describing in particular the Schönheim lower bound on the smallest size of a $(v,k,t)$ covering. Unfortunately the designs they have are limited to fewer than 100 points (and you ask about 120 items).