theorem
  x0,x1 are_connected implies pi_1(X,x0), pi_1(X,x1) are_isomorphic
proof
  set P = the Path of x1,x0;
  assume
A1: x0,x1 are_connected;
  then reconsider
  h = pi_1-iso(P) as Homomorphism of pi_1(X,x0), pi_1(X,x1) by Th50;
  take h;
  thus thesis by A1,Th55;
end;
