theorem Th6:
  g is associative & (g is having_a_unity or len F >= 1) implies g
  "**" (<* d *> ^ F) = g.(d,g "**" F)
proof
A1: len<* d *> = 1 by FINSEQ_1:39;
  assume g is associative &( g is having_a_unity or len F >= 1);
  hence g "**" (<* d *> ^ F) = g.(g "**" <* d *>,g "**" F) by A1,Th5
    .= g.(d,g "**" F) by Lm4;
end;
