Exploring the Complex Logarithm Function for Different Branches

  • Thread starter neginf
  • Start date
  • Tags
    Log
In summary, "Log z for different branches" refers to the natural logarithm of a complex number z, with different values depending on the branch of the complex logarithm function that is used. There are several methods for calculating the natural logarithm, each with its own branch. Different branches are used to define a single-valued function and can affect the result of calculations. The complex logarithm function can also be graphed to visualize the different branches and their ranges for the imaginary part.
  • #1
neginf
56
0

Homework Statement



Show that

(a) log(i^2) = 2*log(i) when log z=ln r + i * theta (r>0 and pi/4 < theta < 9*pi/4)
(b) log(i^2) <> 2*log(i) when log z=ln r + i * theta (r>0 and 3*pi/4 < theta < 11*pi/4)

Homework Equations



log z = ln r + i * theta

The Attempt at a Solution



Got log(i) = i * pi/2
log(i^2)= i * pi.
Are those right ?

Do not know what to do with ranges given for theta.
 
Last edited:
Physics news on Phys.org
  • #2
You're assuming i = eiπ/2, but you also have i = ei(π/2+2π) = ei(π/2+4π) and so on. Now do you see what the problem is getting at?
 

FAQ: Exploring the Complex Logarithm Function for Different Branches

1. What is "Log z for different branches"?

"Log z for different branches" refers to the natural logarithm of a complex number z, with different values depending on the branch of the complex logarithm function that is used.

2. How is "Log z for different branches" calculated?

There are several methods for calculating the natural logarithm of a complex number, each with its own branch of the complex logarithm function. The most common method is to use the principal branch, which is defined as the logarithm with an imaginary part between -π and π. Other branches may have different ranges for the imaginary part.

3. Why are different branches of the complex logarithm function used?

The complex logarithm function is a multivalued function, meaning that there are multiple values that can satisfy the equation e^x = z for a given complex number z. Different branches of the function are used to define a single-valued function that is consistent with the properties of logarithms, such as the power rule and inverse relationship with exponential functions.

4. How do different branches of "Log z for different branches" affect calculations?

The choice of branch for the complex logarithm function can affect the result of calculations involving logarithms. For example, if the principal branch is used, the natural logarithm of a negative real number will have an imaginary part, while other branches may result in a real number solution. It is important to consider the appropriate branch for the specific calculation being performed.

5. Can "Log z for different branches" be graphed?

Yes, the complex logarithm function can be graphed, with each branch represented by a different curve. The principal branch is typically shown as the main curve, while other branches may be shown as dotted lines or different colors. The graph can help visualize the different branches and their ranges for the imaginary part of the natural logarithm.

Back
Top