beginchar("d",.5em#,5cap#/7,0dth#); "delta"; 
picture delta;
path p[];
 save ww,hh;

 ww = w/5; hh = h/5; 
 b := .3ww;

z0 = (3ww,1.1hh);
p0 = fullcircle scaled 2ww shifted z0;
z1 = point 1.5 of p0;
x2 = 5ww - x3 = .5ww;
y2 = 4hh; y3 = 2.5hh;

penpos1(2b,angle(z2-z1)+90);
penpos2(2b,angle(z2-z1));
penpos3(2b,angle(z3-z2)+90);
penstroke z1e{z2-z1}..z2e..{z3-z2}z3e;
pickup pencircle scaled 2b;
draw p0;

delta = currentpicture;
endchar;