
theorem Th10:
  for m,n be non zero Element of NAT,
        M be Matrix of m, F_Real
  holds
    Mx2Tran(M) is bijective
      iff
    M is invertible
proof
  let m,n be non zero Element of NAT,
        M be Matrix of m, F_Real;

  M is invertible iff Det M <> 0. F_Real by LAPLACE:34;
  hence thesis by MATRTOP1:40,42;
end;
