theorem
  for L be add-unital non empty addMagma for x be Element of L holds (mult
  L).(2,x) = x+x
proof
  let L be add-unital non empty addMagma;
  let x be Element of L;
  1+1 = 2;
  hence (mult L).(2,x) = (mult L).(1,x) + x by Def7
    .= x + x by Th49;
end;
