Derivative Notation: Clarifying Confusion

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    Derivative Notation
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Discussion Overview

The discussion revolves around the notation used for derivatives in calculus, specifically examining the expression of derivatives for the function \(f(x) = 2x^\sqrt{2}\). Participants explore various notational forms and their equivalences, addressing common confusions surrounding these representations.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that the notation \(\frac{df(x)}{dx}\) is valid and can be used interchangeably with \(\frac{dy}{dx}\) if \(y = f(x)\).
  • Others argue that while \(\frac{dy}{dx}\) is a standard notation, using \(\frac{df(x)}{dx}\) is also acceptable and may be preferable in certain contexts.
  • A participant mentions that another valid notation for the derivative is \(f'(x)\), suggesting that multiple forms exist.
  • One participant expresses uncertainty about the notation used by their instructor, indicating a potential divergence in teaching styles or conventions.
  • Another participant lists several equivalent forms of derivative notation, emphasizing the flexibility and variety in how derivatives can be expressed.

Areas of Agreement / Disagreement

Participants generally agree that multiple notational forms for derivatives are valid, but there is some uncertainty regarding the preferred usage in different contexts. The discussion remains unresolved regarding which notation is the most appropriate in all situations.

Contextual Notes

Some limitations include the dependence on definitions of variables and functions, as well as the potential for confusion stemming from different instructional approaches to derivative notation.

MacLaddy1
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I am always getting mixed up on derivative notation, so I was just wondering if this below makes sense?

\(f(x) = 2x^\sqrt{2}\)

\(\frac{df(x)}{dx} = 2\frac{d}{dx}x^\sqrt{2}\)

The first should probably just be \(\frac{dy}{dx}\), but I was wondering if the other way would work as well.
 
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MacLaddy said:
I am always getting mixed up on derivative notation, so I was just wondering if this below makes sense?

\(f(x) = 2x^\sqrt{2}\)

\(\frac{df(x)}{dx} = 2\frac{d}{dx}x^\sqrt{2}\)

The first should probably just be \(\frac{dy}{dx}\), but I was wondering if the other way would work as well.

Actually, the way you have it is perfectly fine, and better than $dy/dx$, unless you've defined $y=f(x)$. Another equally valid notation is $f'(x)$.
 
MacLaddy said:
I am always getting mixed up on derivative notation, so I was just wondering if this below makes sense?

\(f(x) = 2x^\sqrt{2}\)

\(\frac{df(x)}{dx} = 2\frac{d}{dx}x^\sqrt{2}\)

The first should probably just be \(\frac{dy}{dx}\), but I was wondering if the other way would work as well.

Using the fact $y=f(x)$ Then you can write $\dfrac{df(x)}{dx}=\dfrac{dy}{dx}$

And yes you can do the above.
 
Thanks Ackbach and dwsmith. I've never seen my instructor do it that way, but it seemed to make sense.
 
If $y=f(x)$, the following are all equivalent:

$$Dy=Df(x)=\frac{d}{dx}\,y=\frac{d}{dx}\,f(x)=y'=f'(x)=\frac{dy}{dx}=\frac{df(x)}{dx}.$$

And I'm probably leaving out a few notations. Hope this doesn't confuse you, but this is the way it's developed.
 

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