Brian Vandenberg
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 Aug 29 accepted Recommendation for a book and other material on dynamical systems Aug 11 comment Recommendation for a book and other material on dynamical systems I just ran across this course, for others who are interested: youtube.com/watch?v=mkfU9zVNGkQ&feature=relmfu Aug 11 answered Reference request: coding in dynamical systems Aug 11 asked Recommendation for a book and other material on dynamical systems Jun 28 comment Online tools for doing symbolic mathematics +1, this looks like an interesting tool. Jun 27 comment Online tools for doing symbolic mathematics It's as though everything lately has been telling me to learn Python. +1 for answering with precisely what I asked for: a web-based app that provides symbolic manipulation that isn't limited to one-liners. Jun 22 comment Using differentials @Noteventhetutorknows - The fractional notation helps give the notion of rates, but it also gives the impression you can just do normal algebraic manipulations on them -- which is definitely not true. It can be done, as Americo Tavares points out, but it must be done very carefully and rigorously. Jun 22 comment Using differentials +1 because it has the potential to generate answers to help explain proper use of differentials. Jun 22 comment Using differentials @Theo - That's fine. What affect does \$\$ have? Jun 22 comment Using differentials @Noteventhetutorknows - re: dubiousness, I was specifically referring to the homogeneous equation I wrote, but what you wrote is fraught with what I would consider to be inappropriate manipulations. The chain rule gives: $\frac{dy}{dx} = \frac{dy}{dt}\frac{dt}{dx}$. Nothing about the chain rule says it's safe or valid to swap denominators as though $\frac{dy}{dt}$ is a simple fraction. Jun 22 comment Using differentials Agreed. When I took my ODE class I just went with it, but as I went back and worked through some of that material years later it occurred to me that the homogeneous equation above is actually a partial differential equation in disguise, of sorts -- hence my addendum with $\frac{dy}{dt}$ (etc). Adding $t$ explicitly seemed to make it easier to 'guess' the solution for those problems. Jun 22 revised Using differentials added 561 characters in body Jun 22 answered Using differentials Jun 13 accepted Online tools for doing symbolic mathematics Jun 9 asked Online tools for doing symbolic mathematics May 16 accepted Convolution & DFTs: How much zero padding is necessary to avoid circular convolution? May 16 comment Convolution & DFTs: How much zero padding is necessary to avoid circular convolution? @joriki - Very good point, thank you. If you want to provide the correct answer and that note as part of your answer, I'll accept it. May 16 comment Convolution & DFTs: How much zero padding is necessary to avoid circular convolution? Scratch that. The answer is $2N - 1$ along each dimension. See the following: cnx.org/content/m10963/latest May 16 asked Convolution & DFTs: How much zero padding is necessary to avoid circular convolution? Apr 28 revised What do $\pi$ and $e$ stand for in the normal distribution formula? added 7 characters in body