
theorem Th25:
  for F being Field holds for a,c being Element of
  F holds for b,d being Element of NonZero F holds ovf(F).(a,b) = ovf(F).(c,d)
  iff omf(F).(a,d) = omf(F).(b,c)
proof
  let F be Field;
  let a,c be Element of F;
  let b,d be Element of NonZero F;
  ovf(F).(a,b) = omf(F).(a,revf(F).b) & ovf(F).(c,d) = omf(F).(c,revf(F).d
  ) by Def2;
  hence thesis by Th5;
end;
