[closed] Winkel Geometric Shape

\documentclass[headheight=19pt]{scrartcl}
%------------------------------------------------------------------------------
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{tikz}
\usetikzlibrary{quotes,babel,angles}
\usetikzlibrary[shapes.geometric] % ConTEXt when using Tik Z
%------------------------------------------------------------------------------
\tikzset{
  winkel/.style={draw=gray,angle eccentricity=.6,angle radius=0.6cm}}
%------------------------------------------------------------------------------
\begin{document}
  \begin{minipage}[t]{0.5\linewidth} 
    Blub. Der Winkel sieht nicht gut aus
    \end{minipage}\hfill
    \raisebox{\dimexpr \ht\strutbox-\totalheight}
    {\begin{minipage}[t]{0.4\linewidth} 
      \begin{tikzpicture}[
    auto,
    mytrapez/.style={
      trapezium,
      draw,
      trapezium left angle=20,
      trapezium right angle=160
    }
  ]
  \node[
    mytrapez,
    minimum width=5cm,
    minimum height=1cm
  ](Trapez){};
  \foreach \placement/\anchor/\text in {%
      below left/bottom left corner/A,
      below right/bottom right corner/B,
      above right/top right corner/C,
      above left/top left corner/D%
    }\coordinate[](\text)at(Trapez.\anchor);
    \pic[pic text=$\alpha$, winkel]{angle=B--A--D};
\path(B)--node{$a$}(A);
\path(D)--node{}(C);
\path(A)--node{}(D);
\path(C)--node{$b$}(B);
\end{tikzpicture}
    \end{minipage}}
\end{document}