Why 1/z dont have antiderivative?

Therefore, the integral of 1/z does not exist. In summary, the derivative of 1/z does not exist because it is not possible to define a function with f'(z)=1/z on the entire complex plane. This means that the integral of 1/z also does not exist. The reason for this is due to the details of the domain of the functions involved.
  • #1
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Homework Statement


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


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The Attempt at a Solution


 
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  • #2
The answer lies in all of the details you haven't said -- things like the domain of the functions under consideration and such.
 
  • #3
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.
 

1. Why doesn't 1/z have an antiderivative?

1/z does not have an antiderivative because it is a complex function, meaning it involves both real and imaginary numbers. The concept of antiderivatives only applies to real functions, and since 1/z is not a real function, it cannot have an antiderivative.

2. Can 1/z be integrated using other methods?

Yes, 1/z can be integrated using a method called Cauchy's integral formula, which involves contour integration. However, this method is more complex and requires a good understanding of complex analysis.

3. Is there a way to approximate the integral of 1/z?

Yes, there are numerical methods that can approximate the integral of 1/z, such as the trapezoidal rule or Simpson's rule. These methods involve breaking up the integral into smaller parts and approximating each part with simpler functions.

4. Are there any special cases where 1/z does have an antiderivative?

There are some special cases where 1/z may have an antiderivative, such as when the function is restricted to a specific domain, or when certain assumptions are made about the function. However, in general, 1/z does not have an antiderivative.

5. Why is it important to understand why 1/z doesn't have an antiderivative?

Understanding why 1/z doesn't have an antiderivative is important in complex analysis, as it highlights the differences between real and complex functions. It also helps in understanding the limitations of integration and the various techniques used to approximate integrals of complex functions.

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