conformal injective map












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I have a conformal, injective map $f: Gsubset mathbb{C} rightarrow mathbb{C} $, G a domain and $D={ z in mathbb{C}: |z|leq 1} subset G $. Furthermore $z_0$ is boundary point of D with $ |f(z_0)|=max_{z in D} |f(z)|$



I want to show, that $ frac{z_0 f'(z_0)}{f(z_0)}$ is real and positive.



You have to consider, that each tangent vector of the curve $f({z:|z|=1})$ at $ f(z_0)$ is orthogonal to the direction of $ argf(z_0)$



Do I have to use that conformal maps are preserving angles, so I can consider the angle of $f^{-1}({z:|z|=1})$
Can somebody help me?










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    $begingroup$


    I have a conformal, injective map $f: Gsubset mathbb{C} rightarrow mathbb{C} $, G a domain and $D={ z in mathbb{C}: |z|leq 1} subset G $. Furthermore $z_0$ is boundary point of D with $ |f(z_0)|=max_{z in D} |f(z)|$



    I want to show, that $ frac{z_0 f'(z_0)}{f(z_0)}$ is real and positive.



    You have to consider, that each tangent vector of the curve $f({z:|z|=1})$ at $ f(z_0)$ is orthogonal to the direction of $ argf(z_0)$



    Do I have to use that conformal maps are preserving angles, so I can consider the angle of $f^{-1}({z:|z|=1})$
    Can somebody help me?










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      I have a conformal, injective map $f: Gsubset mathbb{C} rightarrow mathbb{C} $, G a domain and $D={ z in mathbb{C}: |z|leq 1} subset G $. Furthermore $z_0$ is boundary point of D with $ |f(z_0)|=max_{z in D} |f(z)|$



      I want to show, that $ frac{z_0 f'(z_0)}{f(z_0)}$ is real and positive.



      You have to consider, that each tangent vector of the curve $f({z:|z|=1})$ at $ f(z_0)$ is orthogonal to the direction of $ argf(z_0)$



      Do I have to use that conformal maps are preserving angles, so I can consider the angle of $f^{-1}({z:|z|=1})$
      Can somebody help me?










      share|cite|improve this question









      $endgroup$




      I have a conformal, injective map $f: Gsubset mathbb{C} rightarrow mathbb{C} $, G a domain and $D={ z in mathbb{C}: |z|leq 1} subset G $. Furthermore $z_0$ is boundary point of D with $ |f(z_0)|=max_{z in D} |f(z)|$



      I want to show, that $ frac{z_0 f'(z_0)}{f(z_0)}$ is real and positive.



      You have to consider, that each tangent vector of the curve $f({z:|z|=1})$ at $ f(z_0)$ is orthogonal to the direction of $ argf(z_0)$



      Do I have to use that conformal maps are preserving angles, so I can consider the angle of $f^{-1}({z:|z|=1})$
      Can somebody help me?







      quasiconformal-maps






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 22 at 19:07









      Leon1998Leon1998

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      549






















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