Analyzing the Analyticity of ln (z)

In summary, being analytic means that a function is differentiable at every point in its domain. To prove that ln (z) is analytic, we can use the Cauchy-Riemann equations. The domain of ln (z) is all complex numbers except for 0 and negative real numbers. It cannot be extended to be analytic at 0, but it shares many properties with the natural logarithm function, which is the inverse of the exponential function.
  • #1
Void123
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Homework Statement



How would I prove that [tex]ln (z)[/tex] is analytic?


Homework Equations



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The Attempt at a Solution



I rewrote it as [tex]ln (z) = ln (r) + i\theta[/tex]. But, I'm not quite sure how to apply Cauchy-Riemman conditions here.
 
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  • #2
[tex]\frac{\partial f}{\partial x} = \frac{\partial f}{\partial r}\frac{\partial r}{\partial x} + \frac{\partial f}{\partial \theta}\frac{\partial \theta}{\partial x}[/tex]

if you want to use the polar coordinates. Remember also that CR-equation can be written as

[tex] i \frac{\partial f}{\partial x} = \frac{\partial f}{\partial y}. [/tex]
 

FAQ: Analyzing the Analyticity of ln (z)

What does it mean for ln (z) to be analytic?

Being analytic means that a function is differentiable at every point in its domain. In other words, the function has a derivative at every point and the derivative is continuous.

How do you prove that ln (z) is analytic?

To prove that ln (z) is analytic, we need to show that it is differentiable at every point in its domain. This can be done using the Cauchy-Riemann equations, which state that a function is differentiable if its partial derivatives exist and satisfy certain conditions.

What is the domain of ln (z)?

The domain of ln (z) is all complex numbers except for 0 and negative real numbers. This is because ln (z) is undefined for these values.

Can ln (z) be extended to be analytic at 0?

No, ln (z) cannot be extended to be analytic at 0. This is because the function has a singularity at 0, meaning it is not defined at this point. However, it can be extended to be analytic on the complex plane by excluding the point 0.

What is the relationship between ln (z) and the natural logarithm function?

The natural logarithm function, denoted as ln (x), is the inverse of the exponential function e^x. This means that ln (x) gives the power to which e must be raised to get x. Similarly, ln (z) gives the complex power to which e must be raised to get z, and it shares many of the same properties as the natural logarithm function.

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