Analyzing the Analyticity of ln (z)

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SUMMARY

The function ln(z) is analytic in the complex plane except at the branch cut along the negative real axis. To prove its analyticity, one can express ln(z) in polar coordinates as ln(r) + iθ, where r is the modulus and θ is the argument of z. The Cauchy-Riemann conditions must be applied to verify that the partial derivatives satisfy the necessary criteria for analyticity. Specifically, the equations i(∂f/∂x) = ∂f/∂y must hold true.

PREREQUISITES
  • Understanding of complex functions and their properties
  • Familiarity with polar coordinates in the complex plane
  • Knowledge of Cauchy-Riemann equations
  • Basic calculus, particularly partial derivatives
NEXT STEPS
  • Study the application of Cauchy-Riemann conditions in complex analysis
  • Learn about branch cuts and their implications in complex functions
  • Explore the properties of logarithmic functions in the complex plane
  • Investigate the concept of analyticity and its significance in complex analysis
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Students and professionals in mathematics, particularly those studying complex analysis, as well as educators looking for clear explanations of analyticity in complex functions.

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Homework Statement



How would I prove that [tex]ln (z)[/tex] is analytic?


Homework Equations



...



The Attempt at a Solution



I rewrote it as [tex]ln (z) = ln (r) + i\theta[/tex]. But, I'm not quite sure how to apply Cauchy-Riemman conditions here.
 
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[tex]\frac{\partial f}{\partial x} = \frac{\partial f}{\partial r}\frac{\partial r}{\partial x} + \frac{\partial f}{\partial \theta}\frac{\partial \theta}{\partial x}[/tex]

if you want to use the polar coordinates. Remember also that CR-equation can be written as

[tex]i \frac{\partial f}{\partial x} = \frac{\partial f}{\partial y}.[/tex]
 

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