reserve D for non empty set,
  i,j,k for Nat,
  n,m for Nat,
  r for Real,
  e for real-valued FinSequence;

theorem Th16:
  for D1,D2 being non empty set, M1 being (Matrix of D1),M2 being
Matrix of D2 st M1 = M2 holds for i st i in dom M1 holds Line(M1,i) = Line(M2,i
  )
proof
  let D1,D2 be non empty set, M1 be (Matrix of D1), M2 be Matrix of D2 such
  that
A1: M1 = M2;
  hereby
    let i;
    assume
A2: i in dom M1;
    then Line(M1,i) = M1.i by MATRIX_0:60;
    hence Line(M1,i) = Line(M2,i) by A1,A2,MATRIX_0:60;
  end;
end;
