Product rule in Newton notation?

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Discussion Overview

The discussion centers on the correct representation of the product rule in Newton notation, particularly regarding the use of dots above variables. Participants explore the implications of using different notations and their readability in mathematical expressions.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks about the correct way to express the product rule in Newton notation, specifically if dots should be placed above both variables in the expression d/dt(xy).
  • Another participant suggests using Leibniz notation first and then substituting derivatives with dots, providing the equation d(xy)/dt = dx/dt.y + x.dy/dt = \dot{x}.y + x.\dot{y} as an example.
  • A different participant proposes that using (xy)' might be clearer than placing a single dot above (xy), indicating that \stackrel{\cdotp}{x}\stackrel{\cdotp}{y} would imply the product of the derivatives.
  • A follow-up question is raised about the appropriateness of mixing notations, specifically whether it is acceptable to use (xy)' in a context where dots are predominantly used.
  • Another participant advises sticking with dots or using Leibniz notation throughout, arguing that using a dot over multiple variables can lead to confusion and misinterpretation.

Areas of Agreement / Disagreement

Participants express differing opinions on the clarity and appropriateness of using dots versus the (xy)' notation. There is no consensus on which notation is superior, and the discussion remains unresolved regarding the best practice for representing the product rule in Newton notation.

Contextual Notes

Participants highlight potential readability issues with using dots over multiple variables, suggesting that it may lead to confusion. The discussion does not resolve the question of notation preference or the implications of mixing different notational systems.

volican
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What is the correct way to write the product rule in Newton notation (with the dots above)? It is the LHS I am abit confused with. Eg. Say you have d/dt(xy) would you just put dots above the x and y?
 
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## \stackrel{\cdotp}{(xy)} ## but in this case it would definitely be better to write ##(xy)'## instead.
##\stackrel{\cdotp}{x}\stackrel{\cdotp}{y}## would mean ##\frac{d}{dt}x \cdot \frac{d}{dt}y\,.##
 
Thanks. Why would (xy)' be better to use than the (xy) with a single dot above? In the equation I am working with I have just used all dots, would it be ok to include a single (xy)' ?
 
In this case stay with the dots or use the Leibniz notation everywhere. The dot over more than one variable is simply hard to read. E.g. it could be mistaken by a failure in paper, or just be overlooked.
 

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