theorem
  L1 is being_line & L2 is being_line & L1,L2 are_coplane & L1 <> L2
  implies ex P st L1 c= P & L2 c= P & P is being_plane
proof
  assume that
A1: L1 is being_line and
A2: L2 is being_line & L1,L2 are_coplane & L1 <> L2;
  (ex P st L1 c= P & L2 c= P )& ex x st x in L2 & not x in L1 by A1,A2,Th79
,Th96;
  hence thesis by A1,Th101;
end;
