reserve k,n,i,j for Nat;

theorem Th25:
  for G being Group,f being FinSequence of G holds (Product f)" =
  Product ((Rev f)")
proof
  let G be Group,f be FinSequence of G;
  Product(f ^ (Rev f)")=1_G by Th23;
  then
A1: (Product f) * Product ((Rev f)") = 1_G by GROUP_4:5;
  Product((Rev f)" ^ f)=1_G by Th24;
  then Product ((Rev f)") * (Product f) = 1_G by GROUP_4:5;
  hence thesis by A1,GROUP_1:5;
end;
