What is the Log of a Complex Variable?

In summary, a log of complex variable is a mathematical function that maps a complex number to another complex number. It is the inverse function of the complex exponential function and is defined as ln(r) + iθ, where r is the absolute value of the complex number and θ is the angle of the complex number in polar form. The log of complex variable has properties similar to a logarithm of a real variable and is multi-valued. The principal branch is the main value chosen for the log function, typically with an argument between -π and π. Applications of a log of complex variable include solving equations, evaluating integrals and derivatives, and use in various fields of mathematics, physics, and engineering.
  • #1
baby_1
159
15
what is log of z=X+JY?

Thanks
 
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  • #2
Did you try to find out what it would be??

Here.
 
  • #3
We can always write x+ iy in "polar form": [itex]x+ iy= re^{i\theta}[/itex] where [itex]r= \sqrt{x^2+ y^2}[/itex] and [itex]\theta= arctan(y/x)[/itex].

Then [itex]ln(x+ iy)= ln(re^{i\theta})= ln(r)+ i\theta[/itex]. Of course, because tangent is periodic, with period [itex]\pi[/itex], ln is not a single-valued function:
[itex]ln(x+ iy)= ln(r)+ i(\theta+ n\pi)[/itex] for n any integer.
 
  • #4
Thanks
 
  • #5
ln(x+iy)=ln(r)+i(θ+2*nπ) for n any integer.
 

Related to What is the Log of a Complex Variable?

What is a log of complex variable?

A log of complex variable, also known as a complex logarithm, is a mathematical function that maps a complex number to another complex number. It is the inverse function of the complex exponential function and is used to solve equations involving complex numbers.

How is a log of complex variable defined?

The log of a complex variable is defined as ln(r) + iθ, where r is the absolute value (or modulus) of the complex number and θ is the angle (or argument) of the complex number in polar form.

What are the properties of a log of complex variable?

The log of a complex variable has many properties that are similar to the properties of a logarithm of a real variable. These include the product rule, quotient rule, power rule, and change of base rule. Additionally, the log of a complex variable is multi-valued, meaning that there are infinite possible values for a given complex number.

What is the principal branch of a log of complex variable?

The principal branch of a log of complex variable is the value that is chosen as the "main" value for the log function. This is typically the value with an argument between -π and π, and is often referred to as the "principal value" or "principal logarithm".

What are the applications of a log of complex variable?

The log of complex variable has many applications in mathematics, physics, and engineering. It is used to solve equations involving complex numbers, as well as to evaluate integrals and derivatives of complex functions. It also has applications in signal processing, control systems, and electrical engineering.

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