Complex analysis, graph inequality

In summary, the notation |z|>2 represents a circle with a radius of 2 centered at the origin in the complex plane. This can be seen by converting the inequality into the equation x^2+y^2=4, which is the standard form of a circle.
  • #1
Fellowroot
92
0

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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  • #2
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?
 
  • #3
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.
 
  • #4
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?
 
  • #5
Yes, I see now.

Thank you.
 

Related to Complex analysis, graph inequality

What is complex analysis?

Complex analysis is a branch of mathematics that deals with functions of complex numbers. It studies the properties and behavior of these functions, and how they can be manipulated and used to solve problems in mathematics and other fields.

What is a graph inequality?

A graph inequality is a graphical representation of an inequality equation. It shows the solution set of the equation as a shaded region on a coordinate plane, with the boundary line representing the inequality itself.

What are the applications of complex analysis?

Complex analysis has various applications in mathematics, physics, and engineering. It is used to solve problems in differential equations, Fourier analysis, and fluid dynamics. It is also used in the study of electrical circuits, quantum mechanics, and signal processing.

How do you solve a complex inequality?

To solve a complex inequality, you first need to isolate the variable on one side of the inequality sign. Then, you can graph the inequality on a complex plane and shade the region that represents the solution set. Alternatively, you can solve the inequality algebraically by using the rules of complex numbers.

What are the key concepts in complex analysis?

Some key concepts in complex analysis include the Cauchy-Riemann equations, contour integration, and the Cauchy integral formula. Other important topics include Laurent series, residue theorem, and conformal mapping. These concepts are essential for understanding the behavior of complex functions and their applications.

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