The TikZ and PGF Packages
            Manual for version 3.1.9a
          
          
          
          Part III TikZ ist kein Zeichenprogramm
by Till Tantau
                
                   
              
                \usetikzlibrary {angles,calc,quotes} 
                \begin{tikzpicture}[angle radius=.75cm]
                
                  \node (A) at
                (-2,0)     [red,left]   {$A$};
                  \node (B) at
                ( 3,.5)    [red,right]  {$B$};
                  \node (C) at
                (-2,2)     [blue,left]  {$C$};
                  \node (D) at
                ( 3,2.5)   [blue,right] {$D$};
                  \node (E) at
                (60:-5mm)  [below]      {$E$};
                  \node (F) at
                (60:3.5cm) [above]      {$F$};
                
                  \coordinate (X) at
                (intersection cs:first line={(A)--(B)}, second
                  line={(E)--(F)});
                  \coordinate (Y) at
                (intersection cs:first line={(C)--(D)}, second
                  line={(E)--(F)});
                
                  \path
                    (A) edge
                [red, thick]  (B)
                    (C) edge
                [blue, thick] (D)
                    (E) edge
                [thick]       (F)
                      pic
                ["$\alpha$", draw, fill=yellow]   {angle
                =
                F--X--A}
                      pic
                ["$\beta$",  draw, fill=green!30] {angle
                =
                B--X--F}
                      pic
                ["$\gamma$", draw, fill=yellow]   {angle
                =
                E--Y--D}
                      pic
                ["$\delta$", draw, fill=green!30] {angle
                =
                C--Y--E};
                
                  \node at
                ($ (D)!.5!(B) $) [right=1cm,text width=6cm,rounded corners,fill=red!20,inner sep=1ex]
                    {
                      When
                we
                assume
                that
                $\color{red}AB$
                and
                $\color{blue}CD$
                are
                      parallel, i.\,e., ${\color{red}AB} \mathbin{\|} \color{blue}CD$,
                      then
                $\alpha =
                \gamma$
                and
                $\beta =
                \delta$.
                    };
                \end{tikzpicture}