%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  2. Auflage
%% 
%%  Beispiel 15-02-18 auf Seite 722.
%% 
%%  Copyright (C) 2016 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
defaultfont:="ptmr8r";
warningcheck:=0;
% --- start of displayed preamble in the book ---

% --- end of displayed preamble in the book ---
% %
beginfig(1)
pair A,B,C,D,M;
A=(0,0); B=(2cm,3cm);C=(1cm,0); D=(-1cm,2cm);
M=whatever [A,B];  M=whatever [C,D];
draw A--B; draw C--D;
draw M withpen pencircle scaled 4bp;
endfig;
end;