
theorem Th50:
  for f being Function, x,y being object holds [x,y] in LinTrace f
  iff [{x},y] in Trace f
proof
  let f be Function, x,y be object;
  now
    given v,z being object such that
A1: [x,y] = [v,z] and
A2: [{v},z] in Trace f;
    x = v by A1,XTUPLE_0:1;
    hence [{x},y] in Trace f by A1,A2,XTUPLE_0:1;
  end;
  hence thesis by Def19;
end;
