Inequality and complex numbers

In summary, the conversation revolves around solving a problem where it is required to show an inequality for complex numbers. The first part of the problem is to prove that |e^iz|<=1 for Im(z)>=0 and the second part is to show that if |z|>=3, then there is an inequality that holds for the given equation. The attempt at a solution includes using the equation |e^iz|=e^-b(cosa+isina) and considering the magnitude of the complex number. However, there are some discrepancies and further clarification is needed for the problem to be solved accurately.
  • #1
oddiseas
73
0

Homework Statement

b)show that if |z|>=3 then the following inequality holds

Homework Equations

|z|>=3 now for this to hold b must be <=0 which gives the following:
|e^iz|=e^b(cosa+isina) and taking the magnitude yeilds (e^2b)^1/2
I don't know where to go next.
 
Last edited:
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  • #2
oddiseas said:

Homework Statement



Show that |e^iz|<=1 for Im(z)>=0
b)show that if |z|>=3 then the following inequality holds


Homework Equations





The Attempt at a Solution



|e^iz|=e^-b(cosa+isina)
and since the inmaginery part is always one, the magnitude is always less or equal to one' provided b is <=0. Now the second part i am having trouble with.

You are having trouble with the first part. What are a and b? Are you writing
z = a + ib. If so, you should say so.

This equation |e^iz|=e^-b(cosa+isina) can't be correct because you have a real number on the left and a complex number on the right.

The "inmaginery" (that's imaginary) part of what is one? And why is it 1? Do you know how to compute the magnitude of a complex number?

"provided b is <=0". You are given Im(z) >= 0.

Back to the drawing board.
 
  • #3
Please post the exact problem you are supposed to solve. The following makes no sense:
oddiseas said:
b)show that if |z|>=3 then the following inequality holds
What following inequality? It doesn't appear in either your original post or the edited post.
 

What is inequality in the context of complex numbers?

Inequality in complex numbers refers to the comparison of two complex numbers using the symbols <, >, ≤, or ≥. This comparison is based on the magnitude of the complex numbers, which is determined by their distance from the origin on the complex plane.

How do you graph inequalities in complex numbers?

To graph inequalities in complex numbers, you first plot the complex numbers on the complex plane. Then, you shade the region that satisfies the inequality. For example, if the inequality is z < 3, you would shade the region inside the circle with radius 3 centered at the origin.

What is the relationship between inequalities and absolute values in complex numbers?

The absolute value of a complex number is its distance from the origin on the complex plane. Inequalities in complex numbers are often expressed in terms of absolute values, such as |z| < 3. This means that the distance of z from the origin is less than 3.

How can complex numbers be used to represent inequalities in real-life situations?

Complex numbers can be used to represent inequalities in real-life situations, such as in economics, engineering, and physics. For example, in economics, complex numbers can be used to model supply and demand inequalities. In engineering, they can be used to represent constraints in optimization problems. In physics, they can be used to represent inequalities in electromagnetic fields.

What are some common misconceptions about inequalities in complex numbers?

One common misconception is that inequalities in complex numbers only involve the imaginary part of the complex numbers. In reality, inequalities also consider the real part of the complex numbers. Another misconception is that all complex numbers can be compared using inequalities. This is not true as some complex numbers are not comparable due to their different magnitudes and directions on the complex plane.

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