
theorem Th7:
  for i being Integer,f being FinSequence st 1<=i & i<=len f holds i in dom f
proof
  let i be Integer,f be FinSequence;
  assume that
A1: 1<=i and
A2: i<=len f;
  i is Element of NAT by A1,INT_1:3;
  hence thesis by A1,A2,FINSEQ_3:25;
end;
