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

% --- start of displayed preamble in the book ---
input metaobj
% Circles produced as before

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

newCircle.a(btex start etex);
newCircle.b(btex end etex);
a.c=origin;
b.c-a.c=(3cm,1cm);

defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
nccoil(a)(b)
"doubleline(true)","coilwidth(2mm)",
"angleA(0)", "arrows(-)", "linewidth(1pt)";
drawObj(a,b);
endfig;
end;