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 Let 
where the  's are real numbers satisfying  
 , the  's are real numbers satisfying  
 ;  the integral expression means a complex antiderivative,   and   are complex constants.
The transformation  
   maps the real axis and the upper half-plane conformally onto the closed area bounded by a broken line.  Some vertices of this line may be in the infinity (the corresponding angles are = 0).  When   moves on the real axis from   to  ,   moves along the broken line so that the direction turns the amount   anticlockwise every time
  passes a point  .  If the broken line closes to a polygon, then  
 . 
This transformation is used in solving two-dimensional potential problems.  The parameters   and   are chosen such that the given polygonal domain in the complex  -plane can be obtained. 
A half-trivial example of the transformation is 
which maps the upper half-plane onto the first quadrant of the complex plane.
  
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