% --- start of displayed preamble in the book --- % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) u=1.5pt; labeloffset:=10pt; defaultfont:="ptmb8r"; dotlabel.ulft ("upper left",(100u,100u)); label.urt (btex upper right etex,(100u,100u)); label.llft ("lower left",(100u,100u)); label.lrt (btex $x_1,y_1$ etex,(100u,100u)); draw (50u,100u)--(150u,100u); draw (100u,125u)--(100u,75u); endfig; end;