Total vs Partial Integration: What Are the Key Differences?

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Discussion Overview

The discussion revolves around the differences between total and partial integration, specifically examining the notation used in integrals involving functions of multiple variables. Participants explore the implications of using different differential symbols in the context of integration.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions the difference between the integrals \(\int f(x,y(x)) dx\) and \(\int f(x,y(x)) \partial x\), seeking clarification on how total integrals relate to partial integrals.
  • Another participant expresses unfamiliarity with the use of \(\partial\) in this context, suggesting that it is not a common notation.
  • A different viewpoint states that if the function \(f\) depends only on \(x\), both integrals should yield the same result, assuming the context involves iterated integrals.
  • One participant argues that \(dx\) typically indicates partial integration, while \(\partial x\) serves as a reminder in specific contexts, such as solving exact differential equations.
  • Some participants note that the notation could imply a path integral in cases with multiple independent variables, where one variable is held constant.
  • There is a reference to the CRC Handbook of Chemistry and Physics, suggesting that it may contain relevant information, though participants express uncertainty about its contents.
  • One participant speculates that \(\int f(x,y(x)) \partial x\) might indicate integration with \(y\) held constant, while \(\int f(x,y(x)) dx\) suggests integration over all \(x\)-dependence, but acknowledges the need for more context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the use of \(\partial\) in this context, with multiple competing views and uncertainties regarding the implications of the notation.

Contextual Notes

The discussion highlights limitations in understanding the notation without additional context, and the implications of functional dependence on the integration process remain unresolved.

superg33k
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Hi,

Is there a difference between

\int f(x,y(x)) dx

And

\int f(x,y(x)) \partial x

?

If so, how is the total integral written in terms of partial integrals?

Thanks for your help.
 
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I have never seen \partial used in that way.
 
In both cases, the function f is dependent on x only.

If by partial integration, you mean an iterated integral, then the result of both should be the same.

Either way, the iterated integral uses a total differential dx, not a partial.
 
The dx usually means partial integration. The ∂x is an added reminder of partial integration it is sometimes used when solving exact differential equation as a reminder. Writing y(x) is also a clear indicator of functional dependence, more clear than writing y.
 
HallsofIvy said:
I have never seen \partial used in that way.
Neither have I, and as other posts here point out x is the only independent variable in the OP, so it cannot make any difference.
More generally (when there's another independent variable), it could make sense as a path integral, i.e. along a path where the other independent variable is constant.
 
Have none of you read the CRC Handbook of Chemistry and Physics?
 
I've never seen ##\partial## used that way either (I haven't throughly read the CRC handbook, it seems), but if I had to wager a guess I would suppose that

$$\int f(x,y(x))\partial x$$
is meant to be integrated in only the first argument, holding y=y(x) fixed, while

$$\int f(x,y(x)) dx$$
is meant to be integrated over all of the x-dependence.

But, without some more context, I could be entirely wrong here.
 
Thanks for your help everyone. My question has been answered above and beyond.
 

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