How to tell that 1/(z+2i) is not analytic?

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Discussion Overview

The discussion centers around the expression 1/(z+2i) and whether it is analytic within the circle defined by |z-2|=4. Participants explore the conditions under which a function is considered analytic, particularly focusing on the point -2i.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how to determine if the function is not analytic, specifically in relation to the circle |z-2|=4.
  • Another participant notes that the circle contains the point -2i, where the function does not exist.
  • A follow-up inquiry seeks clarification on how to ascertain that the function does not exist at -2i, suggesting that it may become infinite at that point, indicating non-analyticity.
  • There is a mention of properties of divergence and other analytic properties, such as limits and continuity, as relevant to the discussion of analyticity.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the criteria for determining the analyticity of the function, and there is no consensus on the interpretation of the function's behavior at -2i.

Contextual Notes

Participants reference various properties of analytic functions, but the discussion does not resolve the mathematical steps or assumptions regarding the function's behavior at -2i.

nutcase21
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hi as shown above, i have come across this expression. But i am not sure how to tell if it is not analytic in the circle |z-2|=4, clockwise.
expression: 1/(z+2i)

On top of that, can anyone give me a general idea of how to see if the expression is analytic or not analytic without using the cauchy's equation.

pls help. thx.
 
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Well, that circle contains the point -2i at which f(x) does not even exist.
 
but how do u tell that f(x) does not exist there?

does it mean the function will be come infinite when z=-2i and thus telling us it is not analytic at that point?
 
Last edited:
nutcase21 said:
but how do u tell that f(x) does not exist there?

does it mean the function will be come infinite when z=-2i and thus telling us it is not analytic at that point?

Consider the properties of divergence and also other analytic properties like limits: the limit must be the same from both sides and continuity must hold (among the other properties of analytic functions).
 

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