reserve a,b,c,d,m,x,n,j,k,l for Nat,
  t,u,v,z for Integer,
  f,F for FinSequence of NAT;
reserve p,q,r,s for real number;
reserve a,b,c,d,m,x,n,k,l for Nat,
  t,z for Integer,
  f,F,G for FinSequence of REAL;
reserve q,r,s for real number;
reserve D for set;

theorem Th23:
  b > 1 iff b! > 1
  proof
    thus b > 1 implies b! > 1
    proof
      assume b > 1; then
      b >= 1+1 by NAT_1:13;
      hence thesis by ASYMPT_1:55;
    end;
    thus thesis by ASYMPT_1:56,NEWTON:13;
  end;
