Brian B
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 Nov 5 answered Does fractional part converge in distribution to a uniform random variable? Dec 3 revised A function that is not a derivative simple should have been elementary Dec 3 comment A function that is not a derivative Good catch, Matthew, and so edited. Dec 2 awarded Yearling Dec 2 answered A function that is not a derivative Nov 20 comment Preparing for Spivak I'll never forget all the time I spent figuring out one of Spivak's problems: finding the antiderivative of $\sqrt{\tan(x)}$. Nowadays, Mathematica gets that one automatically. Mar 18 revised Correlation matrix from Covariance matrix fixed to include square root Feb 17 awarded Critic Feb 17 comment How to show that for $|x|<1$, $1+2x+3x^2+\cdots=\frac1{(1-x)^2}$? Definitely untrue for certain values of $n$ and $x$ Feb 12 answered Correlation matrix from Covariance matrix Mar 22 awarded Editor Mar 22 revised Dirac Delta function deleted 3 characters in body Mar 22 comment Dirac Delta function @Carl: Agreed. The original dirac delta was a limit of gaussians, defined in such a way. It is possible to define a point mass functional as a limit of 1-sided kernels as well. I think of these things in functional analytic terms: the $\delta$ defines a functional taking $f$ to its value at the location of the point mass. A limit of even functions is an odder beast, taking $f$ to $f(0)/2$ if the point is on the boundary and $f(0)$ or $0$ otherwise. Note that defining $\delta(x)$ as a limit of even functions has the annoying property that $\int_{(-\infty,0)} f(x) \delta(x) dx = f(0)/2$. Mar 22 answered Dirac Delta function Feb 27 answered Is this function convex? Feb 27 answered How to solve a multiple variable linear equation Feb 24 comment Direct proof that $\pi$ is not constructible If there were such a direct proof wouldn't we have seen far fewer cranks trying to square the circle in the last century or so? Feb 19 awarded Teacher Feb 17 answered Line integration in complex analysis Feb 15 comment Are sines of primes dense in $[-1,1]?$ On distributional principles it sure seems true. Very cool question.