How to Show u(x,y) and v(x,y) are Constant Throughout D?

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Homework Help Overview

The problem involves demonstrating that two functions, u(x,y) and v(x,y), are constant throughout a domain D, given that v is a harmonic conjugate of u and vice versa. The context is rooted in the study of harmonic functions and their properties.

Discussion Character

  • Exploratory, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to apply the definitions of harmonic conjugates and expresses confusion about their reasoning process. Some participants question the meaning of "in one direction" regarding the relationships between the derivatives of u and v.

Discussion Status

The discussion is ongoing, with participants exploring the implications of harmonic conjugates and clarifying the relationships between the functions. A hint has been provided to connect the derivatives, but there is no explicit consensus or resolution yet.

Contextual Notes

There is an indication of potential confusion regarding the definitions and properties of harmonic conjugates, which may affect the understanding of the problem. The original poster expresses a feeling of going in circles, suggesting a need for further clarification.

tylerc1991
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Homework Statement



Suppose v is a harmonic conjugate of u in a domain D, and that u is a harmonic conjugate of v in D. Show how it follows that u(x,y) and v(x,y) are constant throughout D.

The Attempt at a Solution



since u is a harmonic conjugate of v, u_xx + u_yy = 0
also, since v is a harmonic conjugate of u, v_xx + v_yy = 0

u_x = v_y => u_xx = v_yx
u_y = -v_x => u_yy = -v_xy

I think that I am going in circles here. Can someone lend a helping hand with this problem? Thank you so much!
 
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Hint: in one direction u_x=v_y and u_y=(-v_x). In the other direction v_x=u_y and v_y=(-u_x). Put them together.
 
what do you mean in one direction?

do you mean that since u is a harmonic conjugate then that is one direction, and since v is a harmonic conjugate then that is the other direction?
 
tylerc1991 said:
what do you mean in one direction?

do you mean that since u is a harmonic conjugate then that is one direction, and since v is a harmonic conjugate then that is the other direction?

Yes, that's exactly what I mean.
 

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