Proving Inequalities for Complex Analysis Limits

In summary, the conversation discusses how to prove the existence of a delta value such that 0<|z-w|<d implies that the inequality (2^.5)/2 < |h(z)| < 3(2^.5)/2 holds true. The conversation also mentions the use of assumptions and the need to show that a function with a limit satisfies a specific condition.
  • #1
Metahominid
22
0

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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  • #2
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)|.
 

Related to Proving Inequalities for Complex Analysis Limits

What is a limit in complex analysis?

A limit in complex analysis is a mathematical concept that describes the behavior of a function as the input values get closer and closer to a given point. In other words, it is the value that a function approaches as its input values approach a certain point.

How is a limit in complex analysis different from a limit in real analysis?

The main difference between a limit in complex analysis and a limit in real analysis is that in complex analysis, the input values approach a point in the complex plane, while in real analysis, the input values approach a point on the real number line.

What is a complex limit proof?

A complex limit proof is a mathematical argument that uses the definition of a limit to show that a given function approaches a certain value as its input values approach a given point in the complex plane.

What are some common techniques used in complex limit proofs?

Some common techniques used in complex limit proofs include using the definition of a limit, algebraic manipulations, and applying theorems such as the squeeze theorem and the limit laws.

Why is complex analysis important in science?

Complex analysis is important in science because it allows us to study and understand the behavior of complex functions, which are often used to model real-world phenomena in various scientific fields. It also provides powerful tools for solving problems in other areas of mathematics, such as differential equations and number theory.

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