14.3. Polygons
Note that the function (2) maps the real axis onto a polygonal path. We now wish to construct a one-to-one analytic function that maps the upper half plane H onto the interior of a given polygon P. The idea is to tailor a Schwarz-Christoffel transformation to achieve this.
Suppose that the vertices of the polygon P are given by w1,...,wk in the anticlockwise direction. Let us follow the edges of the polygon P. At vertex wj, suppose that we make a right turn of angle θjπ, where −1 < θj < 1, with the convention that θj < 0 denotes a left turn.