theorem
  f|B = g|B implies FinMeet(B,f) = FinMeet(B,g)
proof
  assume
A1: f|B = g|B;
  reconsider f9 = f, g9 = g as Function of A, the carrier of L.:;
A2: FinMeet(B,g) = FinJoin(B,g9);
  L.: is 0_Lattice & FinMeet(B,f) = FinJoin(B,f9) by Th49;
  hence thesis by A1,A2,Th53;
end;
