reserve p,q,r for FinSequence;
reserve u,v,x,y,y1,y2,z for object, A,D,X,Y for set;
reserve i,j,k,l,m,n for Nat;

theorem Th44:
  len Sgm Seg k = k
proof
  card Seg k = k by FINSEQ_1:57;
  hence thesis by Th37;
end;
