How do you prove the partial derivative identity with three variables?

In summary, the conversation discusses the problem of solving the equation f(x,y,z)=0 when each variable can be expressed as a differentiable function of the other two. The goal is to prove that (dx/dy)(dy/dz)(dz/dx)=-1. The conversation includes a helpful hint and a solution approach using differentiation.
  • #1
mj1357
5
0

Homework Statement



Suppose that the equation f(x,y,z)=0 can be solved for each of the three variables as a differentiable function of the other two. Prove that:

(dx/dy)(dy/dz)(dz/dx)=-1

Homework Equations





The Attempt at a Solution


In the case of two variables where one is a function of the other, dy/dx = -(df/dx)/(df/dy), but I can't figure out how this works with 3 variables.
 
Physics news on Phys.org
  • #2
so to get you started, first we know
x=x(y,z)
y=y(z,x)
z=z(x,y)


so fa(x,y,z) = f(x,y,z(x,y))=0 the differentiating w.r.t x gives

df/dx +df/dz(dz/dx)=0
 
  • #3
Thanks. I was able to figure it out from there.
 

1. What is a partial derivative identity?

A partial derivative identity is a mathematical equation that relates the partial derivatives of a function to each other. It is used in multivariable calculus to simplify the process of finding partial derivatives.

2. How is a partial derivative identity different from a regular derivative identity?

A partial derivative identity involves finding the derivative of a multivariable function with respect to one variable while holding all other variables constant. A regular derivative identity involves finding the derivative of a single variable function with respect to that variable.

3. Why are partial derivative identities useful?

Partial derivative identities are useful because they allow us to find partial derivatives of complex multivariable functions quickly and easily. They also help us to identify patterns and relationships between the partial derivatives of a function.

4. How do you use a partial derivative identity to find a partial derivative?

To use a partial derivative identity, you first need to identify the function and the variable you want to take the partial derivative with respect to. Then, substitute the function and variable into the identity and simplify the resulting expression to find the partial derivative.

5. Are there any common partial derivative identities that I should know?

Yes, there are several common partial derivative identities, such as the power rule, product rule, and chain rule. It is important to familiarize yourself with these identities and practice using them in order to become proficient in finding partial derivatives.

Similar threads

  • Calculus and Beyond Homework Help
Replies
10
Views
903
  • Calculus and Beyond Homework Help
Replies
2
Views
959
  • Calculus and Beyond Homework Help
Replies
23
Views
1K
  • Calculus and Beyond Homework Help
Replies
28
Views
2K
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
6
Views
744
  • Calculus and Beyond Homework Help
Replies
3
Views
242
  • Calculus and Beyond Homework Help
Replies
6
Views
836
  • Calculus and Beyond Homework Help
Replies
6
Views
541
  • Calculus and Beyond Homework Help
Replies
13
Views
246
Back
Top