reserve G for Go-board,
  i,j,k,m,n for Nat;

theorem Th5:
  for p being set, D being non empty set for f being non empty
FinSequence of D for g being FinSequence of D st p..f = len f holds (f^g)|--p =
  g
proof
  let p be set, D be non empty set;
  let f being non empty FinSequence of D;
  let g being FinSequence of D such that
A1: p..f = len f;
A2: p in rng f by A1,Th4;
  then
A3: p..(f^g) = len f by A1,FINSEQ_6:6;
  rng f c= rng(f^g) by FINSEQ_1:29;
  hence (f^g) |-- p = (f^g)/^(p..(f^g)) by A2,FINSEQ_5:35
    .= g by A3;
end;
