Proving Inequalities for Complex Analysis Limits

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SUMMARY

The discussion focuses on proving inequalities for limits in complex analysis, specifically for the function h(z) as z approaches w, where lim h(z) = 1+i. The goal is to demonstrate the existence of a delta (d>0) such that 0<|z-w| PREREQUISITES

  • Understanding of limits in complex analysis
  • Familiarity with epsilon-delta definitions
  • Knowledge of inequalities in mathematical proofs
  • Basic proficiency in LaTeX for mathematical notation
NEXT STEPS
  • Study the epsilon-delta definition of limits in complex analysis
  • Learn about the properties of continuous functions in complex domains
  • Explore proofs involving inequalities in real and complex analysis
  • Practice writing mathematical proofs using LaTeX
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Students and educators in mathematics, particularly those focusing on complex analysis, as well as anyone interested in mastering proof techniques involving limits and inequalities.

Metahominid
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Homework Statement


I'm not very good with LaTeX and the reference button seems to broken.
So

Assume lim h(z) = 1+i, as z->w, prove there exists a delta, d>0
s.t. 0<|z-w|<d -> (2^.5)/2 < |h(z)| < 3(2^.5)/2


Homework Equations





The Attempt at a Solution


Kinda been running in circles but from assumption
there exists d>0 s.t. 0<|z-w|<d -> |h(z) - (1+i)| < e (e > 0, epsilon)

So
|h(z)| = |h(z) - (1+i) + (1+i)| <= |h(z) - (1+i)| + |(1+i)|
therefore |h(z)| < e + |1+i| = e + (2^.5)

This seems alright so far but I feel like there is a much better way so
continuing for the other part of the inequality doesn't seem right
 
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Your proof isn't finished yet. You've got:

Metahominid said:
|h(z)| < e + |1+i| = e + (2^.5)

But how did you choose e to obtain [tex]|h(z)|<\frac{3\sqrt{2}}{2}[/tex]?

The proof looks good. But what I would do is show in general that a function [tex]f:D\rightarrow \mathbb{R}[/tex] with [tex]\lim_{x\rightarrow a}{f(x)}=c[/tex] satisfies that there exists a [tex]\delta[/tex] such that [tex]c-\epsilon<f(x)<c+\epsilon[/tex] for all [tex]0<|x-a|<\delta[/tex].
The thing you have to prove follows form this with f(x)=|h(x)|.
 

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