beginfig(89)
u:=3mm;
transform T;
xpart T = ypart T = 0;
xxpart T = 1;
yxpart T = 2;
xypart T = 3;
yypart T = 4;
fill fullcircle scaled 2u transformed T withcolor .8white;
fill fullcircle scaled u shifted (u*dir30) transformed T
withcolor .8white;
fill fullcircle scaled u shifted (u*dir150) transformed T
withcolor .8white;
endfig;
end.