reserve W,X,Y,Z for set,
  f,g for Function,
  a,x,y,z for set;
reserve u,v for Element of Tarski-Class(X),
  A,B,C for Ordinal,
  L for Sequence;

theorem
  Rank A c= Rank succ A
proof
  Rank A in bool Rank A by ZFMISC_1:def 1;
  then Rank A in Rank succ A by Lm2;
  hence thesis by ORDINAL1:def 2;
end;
