theorem Th26:
  F is associative & (i>=1 & j>=1 or F is having_a_unity) implies
  F"**"((i+j)|->d) = F.(F"**"(i|->d),F"**"(j|->d))
proof
  assume
A1: F is associative;
  set p1 = (i|->d),p2 = (j|->d);
  assume i>=1 & j>=1 or F is having_a_unity;
  then len p1 >= 1 & len p2 >= 1 or F is having_a_unity by CARD_1:def 7;
  then F "**"(p1^p2) = F.(F"**"p1,F"**"p2) by A1,FINSOP_1:5;
  hence thesis by FINSEQ_2:123;
end;
