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