theorem
  (M*(A\andB\andC))\iff(M*A)\and(M*B)\and(M*C) in H
  proof
A1: (M*(A\andB\andC))\iff(M*(A\andB))\and(M*C) in H by Def43;
    (M*(A\andB))\iff(M*A)\and(M*B) in H by Def43;
    hence thesis by A1,Th98;
  end;
