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=2.7;
	dot (8,10) scaled sfactor;
	dot (0,2) scaled sfactor;
	dot (2.5,0) scaled sfactor;
	dot (9,0) scaled sfactor;

	pausing:=1;
	fill (2,0)..(0.5,23)..(5,36)..(11,18)..(16,40.5)..
		(25,34)..(25,11)..cycle;
	next; end;
	path a;
	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 2; next;
	draw a scaled sfactor withpen pencircle xscaled 3 rotated 30; next;
	draw a scaled sfactor withpen pencircle xscaled 3 rotated -60; next;
	end