theorem
  a <> 0 implies a /// (A\+\B) = (a///A) \+\ (a///B)
proof
  assume
A1: a <> 0;
  thus a /// (A\+\B) = a ** ((A"")\+\(B"")) by Th35
    .= (a**(A"")) \+\ (a**(B"")) by A1,Th200
    .= (a///A) \+\ (a///B);
end;
