reserve k,n for Nat,
  x,y,z,y1,y2 for object,X,Y for set,
  f,g for Function;
reserve p,q,r,s,t for XFinSequence;
reserve D for set;

theorem Th24: ::: ORDINAL4:2
  rng(p^q) = rng p \/ rng q by ORDINAL4:2;
