% --- start of displayed preamble in the book ---

% --- end of displayed preamble in the book ---
defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
numeric u; u=5mm;
for i:=0 step 10 until 350:
 draw ((i/360)*10u,3u*sind(i))--
      (((i+10)/360)*10u,3u*sind(i+10));
endfor;
endfig;
end;