theorem Th36:
  for A,B,P st 0 < P.A & 0 < P.B holds P.|.B.A = P.|.A.B * P.A / P .B
proof
  let A,B,P;
  assume that
A1: 0 < P.A and
A2: 0 < P.B;
  thus P.|.A.B * P.A / P.B = P.(A /\ B) / P.B by A1,Th29
    .= P.|.B.A by A2,Def6;
end;
