Find Analytic Function F: Cauchy-Riemann Eqns

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Discussion Overview

The discussion revolves around finding an analytic function \( F \) given various forms of \( f \) that satisfy the Cauchy-Riemann equations. Participants explore methods of integration and the conditions under which the functions are analytic, considering both theoretical and practical aspects.

Discussion Character

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

Main Points Raised

  • One participant expresses uncertainty about how to apply the Cauchy-Riemann equations and whether to integrate first or use specific forms for \( du/dx \) and \( du/dy \).
  • Another participant suggests that integration can be approached similarly to calculus.
  • A third participant provides an example of integrating \( f(z) = z-2 \) to find \( F(z) = z^2/2 - 2z + C \), indicating a straightforward integration process.
  • Concerns are raised regarding the second function, which is not entire, prompting a discussion about specifying a domain and the conditions under which the antiderivative is analytic, referencing concepts like independence of path and Morera's theorem.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to take with the Cauchy-Riemann equations, and there are competing views on the conditions for analyticity, particularly regarding the second function.

Contextual Notes

There are limitations in the discussion regarding the assumptions needed for the Cauchy-Riemann equations, the dependence on the definitions of analyticity, and the unresolved mathematical steps related to the second function's domain.

morganmkm
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find an analytic function F where F' = f

f(z) = z-2
f(z) = ((z^4) +1)/(z^2)
f(z) = sinzcosz


I know I have to put these into the cauchy riemann equations but I don't know what to use for my du/dx or du/dy because I am not sure to use x-2 for my du/dx etc or if I am supposed to integrate first. I don't know which parts of the equations fit into the riemann-cauchy equations. My book only gives one example and I don't know how to relate these, please help
 
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Just integrate like in calculus?
 
All these expressions can be handled by ordinary integration (the second one is more difficult).
For example f(z) = z-2, them F(z) = z2/2 - 2z + C.
 
The second function is not entire , so you need to specify a domain. Depending on the level of your class, it would be nice to have an argument for why the antiderivative is analytic (hint, use something like independence of path and Morera's thm.)
 

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