Integral on Circle: Showing $\frac{1}{1-|z|^2}$

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SUMMARY

The integral of the function \(\frac{1}{|1-e^{-i\theta}z|^2}\) over the unit circle \(\mathbb{T}\) evaluates to \(\frac{1}{1-|z|^2}\) for \(z\) within the unit disk. This result is a specific application of the Poisson formula in the unit disk, where the harmonic function considered is the constant function \(f(z) = 1\). The discussion emphasizes the use of normalized Lebesgue measure \(dm\) in the context of this integral.

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Likemath2014
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How I can show the following

[tex]\int _{\mathbb{T}} \frac{1}{|1-e^{-i\theta}z|^2}dm(e^{i\theta})= \frac{1}{1-|z|^2} ,[/tex]
where z is in the unit disc
dm is the normalized Lebesgue measure and
T is the unite circle.
 
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This is a special case of the Poisson formula in the unit disc. Here the harmonic function is the constant function f(z) = 1.
 
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