 reserve x,y,z for object,
   i,j,k,l,n,m for Nat,
   D,E for non empty set;
 reserve M for Matrix of D;
 reserve L for Matrix of E;
 reserve k,t,i,j,m,n for Nat,
   D for non empty set;
 reserve V for free Z_Module;
 reserve a for Element of INT.Ring,
   W for Element of V;
 reserve KL1,KL2,KL3 for Linear_Combination of V,
   X for Subset of V;
 reserve V for finite-rank free Z_Module,
   W for Element of V;
 reserve KL1,KL2,KL3 for Linear_Combination of V,
   X for Subset of V;
 reserve s for FinSequence,
   V1,V2,V3 for finite-rank free Z_Module,
   f,f1,f2 for Function of V1,V2,
   g for Function of V2,V3,
   b1 for OrdBasis of V1,
   b2 for OrdBasis of V2,
   b3 for OrdBasis of V3,
   v1,v2 for Vector of V2,
   v,w for Element of V1;
 reserve p2,F for FinSequence of V1,
   p1,d for FinSequence of INT.Ring,
   KL for Linear_Combination of V1;

theorem ThRank1:
  for V being finite-rank free Z_Module, b being OrdBasis of V
  holds len b = rank V
  proof
    let V be finite-rank free Z_Module, b be OrdBasis of V;
    reconsider R = rng b as Basis of V by defOrdBasis;
    A1: b is one-to-one by defOrdBasis;
    thus len b = card Seg len b by FINSEQ_1:57
    .= card dom b by FINSEQ_1:def 3
    .= card R by A1,CARD_1:70
    .= rank V by ZMODUL03:def 5;
  end;
