reserve a,b,c,h for Integer;
reserve k,m,n for Nat;
reserve i,j,z for Integer;
reserve p for Prime;

theorem Th21:
  for a,b being object, f being FinSequence holds
  (<*a,b*>^f).1 = a & (<*a,b*>^f).2 = b
  proof
    let a,b be object, f be FinSequence;
    set g = <*a,b*>;
    set h = g^f;
    dom g = {1,2} by FINSEQ_1:92;
    then 1 in dom g & 2 in dom g by TARSKI:def 2;
    then h.1 = g.1 & h.2 = g.2 by FINSEQ_1:def 7;
    hence thesis;
  end;
