An algebraic property of complex numbers

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Discussion Overview

The discussion revolves around an algebraic property of complex numbers, specifically examining the relationship between the modulus of the inverse square root of a complex number and the modulus of the complex number itself. The scope includes mathematical reasoning and potential proofs related to complex analysis.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant proposes that for \( z \in \mathbb{C} \), the relationship \( \left| z^{-1/2} \right|^2 = |z^{-1}| = |z|^{-1} = \frac{1}{|z|} \) holds, but expresses difficulty in proving it.
  • Another participant suggests using polar form to facilitate the proof.
  • A third participant emphasizes the importance of specifying that \( z \) is in \( \mathbb{C} \setminus \{0\} \) and notes that the square root function is not defined everywhere, highlighting the ambiguity of the square root in the complex plane due to its multi-valued nature.
  • A later reply indicates that discussions about square roots have been moved to a separate thread, providing a link for reference.

Areas of Agreement / Disagreement

Participants express varying degrees of concern regarding the assumptions and definitions involved in the discussion, particularly about the square root function in the complex context. There is no consensus on the proof or the handling of the square root's ambiguity.

Contextual Notes

Limitations include the need for clarity on the domain of \( z \) and the implications of the multi-valued nature of the square root function in complex analysis.

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I'm guessing that if z\in \mathbb C, then we have

<br /> \left| z^{-1/2} \right|^2 = |z^{-1}| = |z|^{-1} = \frac{1}{|z|}.<br />

Proving this seems to be a real headache though. Is there a quick/easy way to do this?
 
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write z in polar form?
 
Don't mean to nitpick, but remember that it is for z in ℂ\{0} to start with; some profs.

may take away points in an exam if you don't specify this.

But also, remember your square root is not defined everywhere, at least not as a function,

but as a multifunction, since every complex number has two square roots. I mean, the

expression z1/2 is ambiguous until you choose a branch.

Sorry if you already are taking this into account; I am in nitpicking mode, but I

shouldn't take it out on you :) .
 

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