
theorem Th14:
  for S, T being non empty RelStr, s being Element of S, t being
Element of T holds (uparrow [s,t])` = [:(uparrow s)`, the carrier of T:] \/ [:
  the carrier of S, (uparrow t)`:]
proof
  let S, T be non empty RelStr, s be Element of S, t be Element of T;
  thus (uparrow [s,t])` = [:the carrier of S, the carrier of T:] \ uparrow [s,
  t] by YELLOW_3:def 2
    .= [:the carrier of S, the carrier of T:] \ [:uparrow s, uparrow t:] by
YELLOW10:40
    .= [:(uparrow s)`, the carrier of T:] \/ [:the carrier of S, (uparrow t)
  `:] by ZFMISC_1:103;
end;
