theorem Th70:
  [:P,Q:] c= Indices M & card P = card Q implies Det EqSegm(M,P,Q)
  = Det EqSegm(M@,Q,P)
proof
  assume that
A1: [:P,Q:] c= Indices M and
A2: card P = card Q;
  EqSegm(M,P,Q)= Segm(M,P,Q) by A2,Def3
    .=Segm(M@,Q,P)@ by A1,A2,Th62
    .=EqSegm(M@,Q,P)@ by A2,Def3;
  hence thesis by A2,MATRIXR2:43;
end;
