proofing:=1; displaying:=1; openit;
def proofrule(expr a,b) =
	special "rule"; numspecial xpart a; numspecial ypart a;
	numspecial xpart b; numspecial ypart b enddef;
def dot expr a = special " 1"; numspecial xpart a; numspecial ypart a enddef;
def pensquare = makepen ((-.5,-.5)..(.5,-.5)..(.5,.5)..(-.5,.5)..cycle) enddef;

def next =
	showit;
	proofrule ((-10,0),(100,0));
	proofrule ((0,-10),(0,100));
	shipit;
	currentpicture:=nulledges;
enddef;

sfactor=27;
dot (8,10) scaled sfactor;
dot (0,2) scaled sfactor;
dot (2.5,0) scaled sfactor;
dot (9,0) scaled sfactor;

%pausing:=1;
%fill (30,0){right}..(30,30){left}..cycle; next;
path a;
a=(8,10)..(0,2)..(2.5,0){right}..(8,10){up}
 & (8,10){down}..(9,0){right};
%a=(8,10)..tension 1.2..(0,2)..(2.5,0){right}..(8,10){up}
% & (8,10){down}..bounded..(9,0){right};
draw a scaled sfactor withpen pencircle scaled 10 scaled 2; next;
draw a scaled sfactor withpen pencircle scaled 10 xscaled 3 rotated 30; next;
draw a scaled sfactor withpen pencircle scaled 10 xscaled 3 rotated -60; next;
end