reserve x for set,
  i,j,k,n for Nat,
  K for Field;
reserve a,b,c,d for Element of K;
reserve D for non empty set;

theorem
  for x,y,z being Element of D for f being FinSequence of D st f = <*x,y
  ,z*> holds Rev f = <*z,y,x*>
proof
  let x,y,z be Element of D;
  let f be FinSequence of D;
  reconsider h = <*y,z*> as FinSequence of D;
  assume f = <*x,y,z*>;
  then
A1: f = <*x*>^h by FINSEQ_1:43;
  Rev h = <*z,y*> by FINSEQ_5:61;
  hence thesis by A1,FINSEQ_6:24;
end;
