Solving a PDE for z(x,y) with Total and 2nd Derivatives: Step-by-Step Guide

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Discussion Overview

The discussion revolves around solving a partial differential equation (PDE) for the function z(x,y), where y is also a function of x. Participants explore various methods and considerations for approaching the problem, including the implications of total and second derivatives, and the absence of boundary or initial conditions.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant describes z(x,y) as a function of x and y, noting that y is dependent on x, leading to the definitions of total and second derivatives y'(x) and y"(x).
  • Another participant suggests using the separation of variables method, proposing the assumption Z(x,y) = X(x)Y(y).
  • A third participant provides links to a tutorial and lecture notes on the separation of variables technique.
  • One participant expresses concern that the total derivative terms y'(x) and y"(x) complicate the separation of variables approach.
  • Another participant questions whether the problem should involve a system of coupled equations, given the need for two functions.
  • A later reply clarifies that the goal is to find a single function Z(x,y), while also noting that the structure of the PDE resembles a wave equation, albeit with complications introduced by additional terms.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to solve the PDE, with multiple competing views on the methods and implications of the problem remaining unresolved.

Contextual Notes

The discussion lacks boundary or initial conditions, which may affect the solvability and approach to the PDE. There are also unresolved questions regarding the nature of the derivatives involved and the potential need for coupled equations.

chacal10
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TL;DR
I have not been able to solve this PDE; need some help pls
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as you can see, z(x,y) is a function of x, y; and y is a function of x, therefore y'(x) is the total derivative of "y" respect to "x", and y"(x) is the 2nd derivative. y'(x)^2 is just the square of the derivative of y respect to x

I don't have boundary or initial conditions, so you can make up any if that simplifies finding the solution

Thank you !
 
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Have you tried the separation of variables strategy?

Assume ##Z(x,y) = X(x)Y(y)##
 
Let me try that. I think the problem with separation of variables is the total derivative terms y'(x) and y"(x) that multiply the partial derivatives
 
I don't know much about PDEs but I see you're looking for two functions here, shouldn't there be a system of coupled equations instead of just one?
 
@TheDS1337
Is actually one function Z(x,y), but "y" itself is a function of "x" (unknown at this time)
What I am trying to find as the "solution" to this PDE is Z(x,y), i.e. something like "...Z(x,y) = A*cos(y-wx) + exp(-y*x)..." or something like that.
Note that the first 2 parts of the PDE look suspiciously close to a wave equation (if you replace "x" by "t"), but then the 3rd part messes the whole thing up

Thank you all!
 

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