How does the chain rule apply to partial derivatives?

In summary, the conversation discusses the correct equation for solving for the partial derivative of z with respect to x, given that u=g(x,y) and v=h(x). It is given as \frac{\partial z}{\partial x}= \frac{\partial z}{\partial u}\frac{\partial g}{\partial x}+ \frac{\partial z}{\partial v}\frac{dh}{dx}+ \frac{\partial z}{\partial x}. One participant expresses confusion about this equation, but it is confirmed to be correct by another participant.
  • #1
jegues
1,097
3

Homework Statement


See figure.


Homework Equations





The Attempt at a Solution



Here's what I got,

[tex]\frac{ \partial z}{\partial x} = \left( \frac{\partial z}{\partial u} \cdot \frac{\partial u}{\partial x} \right) + \left( \frac{\partial z}{\partial v} \cdot \frac{\partial v}{\partial x} \right) + \left( \frac{\partial z}{\partial x}\right)[/tex]

Is this correct?
 

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  • #2
I don't know much about partial derivatives, but it seems weird that what you're solving for (dz/dx), is also your last term on the right side of the equivalency.

EDIT: Upon further review, looks like I just don't know enough. Sorry for this not-so-helpful post :(
 
  • #3
Yes, that is correct- although since you are given that u= g(x,y) and v= h(x), it would be better to write
[tex]\frac{\partial z}{\partial x}= \frac{\partial z}{\partial u}\frac{\partial g}{\partial x}+ \frac{\partial z}{\partial v}\frac{dh}{dx}+ \frac{\partial z}{\partial x}[/tex]
 
  • #4
HallsofIvy,
That's exactly what I got, but it bothered me that, since [tex]\frac{\partial z}{\partial x}[/tex] appears on both sides, there doesn't seem to be any way to get an explicit value for this partial.
 

FAQ: How does the chain rule apply to partial derivatives?

What is the Partial Derivative Chain Rule?

The Partial Derivative Chain Rule is a mathematical rule used to calculate the partial derivative of a function with respect to a specific variable, while taking into account the effect of other variables on that function.

How is the Partial Derivative Chain Rule used?

The Partial Derivative Chain Rule is used to find the rate of change of a function with respect to a specific variable, while keeping all other variables constant. It is commonly used in multivariable calculus to solve optimization problems and to calculate gradients.

What is the formula for the Partial Derivative Chain Rule?

The formula for the Partial Derivative Chain Rule is d(uv)/dx = u * dv/dx + v * du/dx, where u and v are functions of x and d/dx represents the partial derivative with respect to x.

When should the Partial Derivative Chain Rule be applied?

The Partial Derivative Chain Rule should be applied when a function has multiple variables and the partial derivative of one variable is affected by the other variables. It allows for a more accurate calculation of the partial derivative in these cases.

What are some real-world applications of the Partial Derivative Chain Rule?

The Partial Derivative Chain Rule has many real-world applications, including in economics for calculating marginal effects and elasticity, in physics for calculating rates of change in multiple variables, and in engineering for optimizing complex systems with multiple variables.

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