Why 1/z dont have antiderivative?

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SUMMARY

The function \( \frac{1}{z} \) does not possess an antiderivative across the entire complex plane due to the nature of its domain. While the derivative of \( \log z \) is \( \frac{1}{z} \), the logarithm is only defined on the principal branch, which excludes certain points in the complex plane. Consequently, there is no single function \( f(z) \) such that \( f'(z) = \frac{1}{z} \) for all \( z \in \mathbb{C} \).

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  • Understanding of complex analysis concepts, particularly the complex plane.
  • Familiarity with the properties of logarithmic functions, specifically the principal branch of \( \log z \).
  • Knowledge of derivatives and antiderivatives in the context of complex functions.
  • Basic understanding of singularities and branch cuts in complex analysis.
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  • Study the properties of the principal branch of the logarithm in complex analysis.
  • Learn about singularities and branch cuts in complex functions.
  • Explore the concept of primitives and antiderivatives in the context of complex variables.
  • Investigate the implications of the Cauchy Integral Theorem on functions like \( \frac{1}{z} \).
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Homework Statement


why \frac{1}{z} don't have derivative? i know that ( \log z )'=\frac{1}{z} so why \int \frac{1}{z} \mbox{d} z don't exist?


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The Attempt at a Solution


 
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The answer lies in all of the details you haven't said -- things like the domain of the functions under consideration and such.
 
I just did this on an assignment, so I can answer this question :D

Note that we usually talk about log(z) as being the principal branch; then it is only defined on the cut-plane. It turns out that you cannot define a function such that f'(z)=1/z on the whole complex plane. In other words 1/z does not have a primitive on all of C.
 

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