reserve c for Complex;
reserve r for Real;
reserve m,n for Nat;
reserve f for complex-valued Function;
reserve f,g for differentiable Function of REAL,REAL;
reserve L for non empty ZeroStr;
reserve x for Element of L;

theorem Th27:
  x <> 0.L implies len seq(n,x) = n+1
  proof
    assume
A1: x <> 0.L;
    set p = seq(n,x);
    for m st m is_at_least_length_of p holds n+1 <= m
    proof
      let m such that
A2:   m is_at_least_length_of p;
      p.n = x by Th24;
      hence n+1 <= m by A1,A2,NAT_1:13;
    end;
    hence thesis by Th26,ALGSEQ_1:def 3;
  end;
