Understanding the Straight Chain Rule: Help Needed!

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Discussion Overview

The discussion revolves around the application of the chain rule in calculus, specifically in the context of differentiating the expression (dy/dx)^2. Participants explore the correct application of the chain rule and the implications of differentiating with respect to different variables.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant presents a differentiation problem involving (dy/dx)^2 and applies the chain rule, arriving at the expression 2 (dy/dx) (d2y/dx2).
  • The same participant notes a discrepancy with a paper that suggests the (dy/dx) term disappears, leading to the expression 2 (d2y/dx2).
  • Another participant requests clarification in LaTex format to better understand the question posed.
  • A later reply suggests that if the paper was referenced correctly, it may be incorrect, implying a potential misunderstanding in the differentiation process.
  • In a subsequent post, the original poster acknowledges a mistake, realizing that the paper was differentiating with respect to y rather than x.

Areas of Agreement / Disagreement

The discussion reflects a progression from confusion to clarity, with initial disagreement about the application of the chain rule. Ultimately, the original poster concedes to having misunderstood the context of the paper, indicating a resolution to their specific confusion but not necessarily to the broader discussion of the chain rule application.

Contextual Notes

The discussion highlights the importance of variable differentiation and the potential for misunderstanding when applying calculus rules. There may be limitations in the clarity of the initial question and the assumptions made about the differentiation context.

Mgarrettny
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Can someone help me out with what I believe who.d be a straight chain rule application?

D/dx (dy/dx)^2

I would think, applying the chain rule, you get

2 (dy/dx) d/dx (dy/dx) = 2 (dy/dx) (d2y/dx2)

But, from the papers I checked, the (dy/dx) in the answer goes away, leaving just

2 (d2y/dx2)

What am I missing?
 
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Can you rewrite your question in LaTex? I don't quite follow what you are saying.
 
Mgarrettny said:
Can someone help me out with what I believe who.d be a straight chain rule application?

D/dx (dy/dx)^2

I would think, applying the chain rule, you get

2 (dy/dx) d/dx (dy/dx) = 2 (dy/dx) (d2y/dx2)

But, from the papers I checked, the (dy/dx) in the answer goes away, leaving just

2 (d2y/dx2)

What am I missing?

If you have referred correctly to the paper, the paper is wrong.
 
Sorry everyone, ignore this.
 
Thanks arildo, especially for the light speed reply. The paper was right, it was I who was wrong. I did not realize the paper was differentiating by y not x. Mea culpa.
 

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