What is the solution for a PDE using method of characteristics?

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Homework Help Overview

The discussion revolves around solving a partial differential equation (PDE) using the method of characteristics. The specific equation under consideration is y ∂u/∂x - x ∂u/∂y = 1, with the initial condition u(x,0) = 0 for 0 < x < ∞.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to derive the characteristic equations, starting with ∂y/∂x = x/y, leading to the expression y² + x² = k. However, they express difficulty in progressing to the next part of the solution, specifically in finding ∂u/∂x = 1/y. Other participants engage by correcting and discussing the characteristic equations, noting variations in the formulation.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the characteristic equations. Some guidance has been offered in the form of corrections to the equations, but there is no explicit consensus on how to proceed with the solution.

Contextual Notes

Participants are navigating through the complexities of the method of characteristics and are addressing potential misunderstandings in the formulation of the equations. There is an acknowledgment of the initial condition and the challenges it presents in the context of the problem.

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Homework Statement



solve using method of characteristics
[tex] <br /> y \frac{ \partial u}{ \partial x} - x \frac{ \partial u}{ \partial y}= 1<br /> [/tex] where u(x,0) = 0 for 0<x<infinity

The Attempt at a Solution



[tex] <br /> \frac{ \partial y}{ \partial x} = \frac{x}{y}<br /> [/tex] which gives [tex]y^2+x^2= k[/tex] the projected characteristic. but its the second part that is giving me trouble when i go to find [tex] <br /> \frac{ \partial u}{ \partial x} = \frac{1}{y}<br /> [/tex] which doesn't work out right...any suggestion anyone?
 
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hi gtfitzpatrick! :smile:

(have a curly d: ∂ :wink:)

∂y/∂x = x/y gives y2 minus x2 = k :wink:
 
tiny-tim said:
hi gtfitzpatrick! :smile:

(have a curly d: ∂ :wink:)

∂y/∂x = x/y gives y2 minus x2 = k :wink:


my mistake it should have read

∂y/∂x = -x/y gives y2 + x2 = k

but don't know how to work the second part?
 
oh and hi back :smile:
 

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