
theorem
  for f being FinSequence of TOP-REAL 2 st f is being_S-Seq holds
  R_Cut (f,f/.len f) = f
proof
  let f be FinSequence of TOP-REAL 2;
  assume
A1: f is being_S-Seq;
  then
A2: 2 <= len f by TOPREAL1:def 8;
  then
A3: f/.len f in L~f by JORDAN3:1;
A4: f/.len f = (Rev f)/.1 by A2,CARD_1:27,FINSEQ_5:65;
  thus R_Cut (f,f/.len f) = Rev Rev R_Cut (f,f/.len f)
    .= Rev L_Cut(Rev f,f/.len f) by A1,A3,JORDAN3:22
    .= Rev Rev f by A1,A4,Th27
    .= f;
end;
