Implicit Differentiation z=f(x/y) meaning

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Discussion Overview

The discussion revolves around the interpretation of the expression z = ƒ(x/y) and the process of finding the partial derivatives ∂z/∂x and ∂z/∂y. Participants explore the application of implicit differentiation and the chain rule in this context.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Some participants express uncertainty about the meaning of z = ƒ(x/y) and how to derive the partial derivatives from this expression.
  • One participant suggests using a simple function for f, such as f(X) = X^2, to clarify the concept.
  • Another participant explains that z is a function of the quotient x/y and provides an example function for z.
  • There is a question about the correct application of the chain rule, with a participant unsure about the notation and variables involved.
  • A later reply confirms the use of u = x/y and presents a formula for ∂z/∂x, indicating that ∂z/∂u = f' is a reasonable assumption.

Areas of Agreement / Disagreement

Participants generally agree on the interpretation of z as a function of the quotient x/y and the application of the chain rule, but there remains uncertainty about the details of the differentiation process and the notation used.

Contextual Notes

Participants express confusion regarding the application of the chain rule and the definitions of certain variables, which may affect their understanding of the differentiation process.

xoxomae
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Mod note: Moved from the Homework section
1. Homework Statement

This might seem like a stupid question but I'm unsure what z= ƒ(x/y) means? I'm not sure how I would find ∂z/∂x , ∂z/∂y just from this statement either.

Thank you

Homework Equations

The Attempt at a Solution

 
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xoxomae said:

Homework Statement


This might seem like a stupid question but I'm unsure what z= ƒ(x/y) means? I'm not sure how I would find ∂z/∂x , ∂z/∂y just from this statement either.

Thank you

Homework Equations

The Attempt at a Solution


You could try taking ##f## to be some simple function. For example ##f(X) = X^2##, where I've used ##X## to define the function to avoid confusion with ##x, y##.
 
xoxomae said:
Mod note: Moved from the Homework section
1. Homework Statement

This might seem like a stupid question but I'm unsure what z= ƒ(x/y) means? I'm not sure how I would find ∂z/∂x , ∂z/∂y just from this statement either.
It means that z is a function of the quotient x/y. For example, ##z = (x/y)^2 + 3(x/y)##

To find the partial derivatives, you'll need to use the chain rule.
 
I'm sorry, I'm just really unsure how to apply the chain rule. So is ∂z/∂t = ∂/∂x(x/y) * F' ? But I'm unsure how to find all the other ones. I have the solutions attached to this post but I have no idea how to get them.
Thank You
 

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xoxomae said:
I'm sorry, I'm just really unsure how to apply the chain rule. So is ∂z/∂t = ∂/∂x(x/y) * F' ? But I'm unsure how to find all the other ones. I have the solutions attached to this post but I have no idea how to get them.
Thank You
What are ##t## and ##F##?

Can you calculate ##\frac{\partial z}{\partial x}## if ##z=f(u(x,y))## where ##u## is a function of ##x## and ##y##?
 
So i would let u=x/y so then

$$ \frac{\partial z}{\partial x} = \frac{\partial z }{\partial u} \frac{\partial u }{\partial x} = \frac{f'}{y} $$

cause I'm guessing $$\frac{\partial z }{\partial u} = f'$$ or am i completely wrong?
 
That's right.
 

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