How Do I Solve Complex Equations with Different Lambda Values?

In summary, complex numbers are different from real numbers as they have both a real and imaginary component. Adding and subtracting complex numbers involves combining the real and imaginary components separately. Multiplying and dividing complex numbers can be done using the FOIL method and the complex conjugate of the denominator. The complex conjugate of a complex number is the same number with the sign of the imaginary component changed. In real life, complex numbers are used in fields such as engineering, physics, and economics to describe and analyze oscillatory systems and complex systems.
  • #1
Banker
27
1

Homework Statement


Question 3.b. - http://imgur.com/ztLiRvx

Homework Equations


For the sake of simplicity, let's assume that lambda = x.

The Attempt at a Solution


I tried equating the real an imaginary parts of arctan(1/4).
Real: x/2 + 3 = 4. This gives x = 2.
Imaginary: x/2 - 3 = 1. This gives x = 8.
I'm getting two different values of x(lambda).
 
Physics news on Phys.org
  • #2
Banker said:

Homework Statement


Question 3.b. - http://imgur.com/ztLiRvx

Homework Equations


For the sake of simplicity, let's assume that lambda = x.

The Attempt at a Solution


I tried equating the real an imaginary parts of arctan(1/4).
Real: x/2 + 3 = 4. This gives x = 2.
Imaginary: x/2 - 3 = 1. This gives x = 8.
I'm getting two different values of x(lambda).
##\displaystyle arg(z) = tan^{-1}\left(\frac{Im(z)}{Re(z)}\right) \ ##

so you only know the ratio of the real to imaginary parts. It's not that the real part is 4 and the imaginary part is 1 .
 
  • Like
Likes Banker
  • #3
Banker said:

Homework Statement


Question 3.b. - http://imgur.com/ztLiRvx

Homework Equations


For the sake of simplicity, let's assume that lambda = x.

The Attempt at a Solution


I tried equating the real an imaginary parts of arctan(1/4).
?
I don't know what you're doing. arctan(1/4) means the angle (number) whose tangent is 1/4.
Banker said:
Real: x/2 + 3 = 4. This gives x = 2.
Imaginary: x/2 - 3 = 1. This gives x = 8.
No.
If z = x I iy, then arg(z) = arctan(y/x).

Use the result from part a of this problem and the above to find ##\lambda## -- there is a single value.
Banker said:
I'm getting two different values of x(lambda).
 
  • Like
Likes Banker
  • #4
@Mark44 In my original attempt, I tried to reverse the process you mentioned, but as Sammy pointed out, it only tells the ratio.
So I then divided the equations for the imaginary and real parts in part 'a' and got 10 as my answer. So that will give 68 as the answer to the second part of 3.b, right?
 
  • #5
Banker said:
@Mark44 In my original attempt, I tried to reverse the process you mentioned, but as Sammy pointed out, it only tells the ratio.
So I then divided the equations for the imaginary and real parts in part 'a' and got 10 as my answer. So that will give 68 as the answer to the second part of 3.b, right?
Yes, those are correct, although we generally like to see details of how you worked it out. That makes it easier for us to check your answer.

By the way, if you click on the big " Σ " in the blue menu bar at top of the message window, you will have easy access to many characters, including λ . Otherwise, it would be wise to use almost any other letter to represent λ, other than x, y, or z . Upper case L would have been a good choice.
 
Last edited:
  • #7

Related to How Do I Solve Complex Equations with Different Lambda Values?

1. What are complex numbers and how are they different from real numbers?

Complex numbers are numbers with both a real and imaginary component. The real component is a normal number, while the imaginary component is a multiple of the imaginary unit, i. Real numbers can be plotted on a number line, while complex numbers are plotted on a complex plane with the real component on the x-axis and the imaginary component on the y-axis.

2. How do you add and subtract complex numbers?

To add or subtract complex numbers, simply combine the real components and combine the imaginary components separately. For example, (3 + 2i) + (5 - 4i) = (3 + 5) + (2i - 4i) = 8 - 2i. Similarly, (3 + 2i) - (5 - 4i) = (3 - 5) + (2i + 4i) = -2 + 6i.

3. Can you multiply and divide complex numbers?

Yes, you can multiply and divide complex numbers using the FOIL method (First, Outer, Inner, Last). For example, (3 + 2i)(5 - 4i) = 15 - 12i + 10i - 8i^2 = 15 - 2i - 8(-1) = 23 - 2i. To divide, you can multiply by the complex conjugate of the denominator to eliminate the imaginary component in the denominator.

4. What is the complex conjugate?

The complex conjugate of a complex number is the same number with the sign of the imaginary component changed. For example, the complex conjugate of 3 + 2i is 3 - 2i. This is important in dividing complex numbers, as it allows us to eliminate the imaginary component in the denominator.

5. How are complex numbers used in real life?

Complex numbers are used in many fields, such as engineering, physics, and economics. They are particularly useful in describing and analyzing oscillatory systems, such as electrical circuits and sound waves. They are also used in signal processing to analyze and filter signals. In economics, complex numbers are used in the study of complex systems, such as financial markets and population dynamics.

Similar threads

  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
1K
  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
721
  • Calculus and Beyond Homework Help
Replies
2
Views
569
Replies
4
Views
772
  • Calculus and Beyond Homework Help
Replies
17
Views
897
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
Back
Top