Complex analysis, graph inequality

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Homework Help Overview

The discussion revolves around the graphing of the inequality |Re(z)| > 2, where z is a complex number represented as z = x + iy. Participants are exploring the implications of this inequality in the context of complex analysis.

Discussion Character

  • Conceptual clarification, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants discuss the meaning of the notation | |, questioning whether it represents absolute value or modulus. There is confusion regarding the graphical representation of the inequality, with attempts to relate it to known geometric shapes such as circles and lines.

Discussion Status

Some participants have provided clarifications regarding the nature of the inequality, distinguishing between the representations of |x| > 2 and |z| > 2. There is an ongoing exploration of the correct interpretation of the graph and the boundaries involved.

Contextual Notes

Participants express uncertainty about how to test values for the inequality and how to properly shade the graph. There is mention of confusion stemming from different forms of inequalities and their graphical representations.

Fellowroot
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Homework Statement



Sketch the graph

|Re(z)|>2

Homework Equations



z=x+iy

The Attempt at a Solution



|Re(z)|>2

|Re(x+iy)|>2

|x|>2

|x-0|>2, this is a circle centered at zero with radius 2

4. My question

What I'm having a hard time with is the | | notation.
Is this the absolute value, or modulus, or something else.

Wolfram Alpha says its an absolute value graph (that I understand) but my books says this is the form of a circle. Which is it?
http://www.wolframalpha.com/input/?i=|Re(z)|>2

I graphed a circle on my paper r=2 at (0,0) but I don't know which part to shade, the inside of the circle or the outside? How can I plug in numbers to test True and False? I know how to graph inequalities in real but complex I'm having trouble with.

Thanks.
 
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I have no idea what Wolfram Alpha is thinking about. Ignore it, please? || is modulus or absolute value. They are really the same thing. |x|>2 is perfectly correct. But it's not a circle at all. x=2 is a line, x=(-2) is another line. Those are the boundaries of your region, yes?
 
I now see why |x|>2 is NOT a circle.

I got it confused with this formula |z-z[itex]_{0}[/itex]|=[itex]\rho[/itex]

Because |z|>2 is a circle.

And I still have a hard time seeing why |z|>2 is a circle.
 
Fellowroot said:
I now see why |x|>2 is NOT a circle.

I got it confused with this formula |z-z[itex]_{0}[/itex]|=[itex]\rho[/itex]

Because |z|>2 is a circle.

And I still have a hard time seeing why |z|>2 is a circle.

|z|=|x+iy|=sqrt(x^2+y^2). Do you know that? sqrt(x^2+y^2)=2 is the same as x^2+y^2=4. Do you see why x^2+y^2=4 is a circle?
 
Yes, I see now.

Thank you.
 

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