theorem Th80:
  for P be Path of a, b, Q be constant Path of b, b st a, b
  are_connected holds P + Q, P are_homotopic
proof
  let P be Path of a, b, Q be constant Path of b, b such that
A1: a,b are_connected;
  RePar (P, 1RP) = P + Q by A1,Th50;
  hence thesis by A1,Th45,Th47;
end;
