reserve x,y,z for set;
reserve f,f1,f2,f3 for FinSequence,
  p,p1,p2,p3 for set,
  i,k for Nat;
reserve D for non empty set,
  p,p1,p2,p3 for Element of D,
  f,f1,f2 for FinSequence of D;

theorem Th87:
  f just_once_values p implies Rev(f:-p) = Rev f -:p
proof
  assume
A1: f just_once_values p;
  then
A2: p in rng f by FINSEQ_4:5;
  then
A3: p in rng Rev f by FINSEQ_5:57;
  thus Rev(f:-p) = Rev(<*p*>^(f|--p)) by A2,Th41
    .= Rev(f|--p)^<*p*> by Th24
    .= (Rev f -|p)^<*p*> by A1,Th86
    .= Rev f -:p by A3,Th40;
end;
