theorem
  Funcs(X, Y --> Z) = Y --> Funcs(X,Z)
proof
A1: Y = dom (Y --> Z);
A2: now
    let x be object;
    assume
A3: x in Y;
    then Funcs(X, Y --> Z).x = Funcs(X, (Y --> Z).x) by A1,Def8;
    hence Funcs(X, Y --> Z).x = Funcs(X,Z) by A3,FUNCOP_1:7;
  end;
  dom Funcs(X, Y --> Z) = dom (Y --> Z) by Def8;
  hence thesis by A2,FUNCOP_1:11;
end;
