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  • 0 posts edited
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  • 49 votes cast
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
Apr
21
answered Good Book On Combinatorics
Apr
21
comment Is this a positive semi- definite matrix
The OP didn't ask about 2x2 matrices.