theorem Th47:
  q in K & q in M & K is being_line & M is being_line implies K,M,
  M is_coplanar & M,K,M is_coplanar & M,M,K is_coplanar
proof
  assume q in K & q in M & K is being_line & M is being_line;
  then ex X st K c= X & M c= X & X is being_plane by Th38;
  hence thesis;
end;
