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etotheipi
This is more of a "housekeeping" question, though I haven't studied much in the way of infinitesimals so apologies in advance for my lack of rigour!
As far as I'm aware, an infinitesimal can be thought of as a small change in some quantity. Changes can be either positive or negative, so subsequently it also seems reasonable for ##dx## to potentially represent a negative change. Of course, there is no ambiguity since we always consider one infinitesimal in conjunction with another (e.g. ##dy=-3 dx##) so the signs "cancel appropriately".
In thermodynamics, for instance, it's common to use infinitesimals like ##dU## and ##dV## (I'm not going to worry about the problems with đQ/dQ etc, since that's a different story!), and evidently ##dU## and ##dV## can take both positive and negative values.
Thank you.
As far as I'm aware, an infinitesimal can be thought of as a small change in some quantity. Changes can be either positive or negative, so subsequently it also seems reasonable for ##dx## to potentially represent a negative change. Of course, there is no ambiguity since we always consider one infinitesimal in conjunction with another (e.g. ##dy=-3 dx##) so the signs "cancel appropriately".
In thermodynamics, for instance, it's common to use infinitesimals like ##dU## and ##dV## (I'm not going to worry about the problems with đQ/dQ etc, since that's a different story!), and evidently ##dU## and ##dV## can take both positive and negative values.
Thank you.
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