reserve o,m for set;
reserve C for Cartesian_category;
reserve a,b,c,d,e,s for Object of C;

theorem Th45:
  for a,b being Object of c1Cat*(o,m) holds a = b
proof
  let a,b be Object of c1Cat*(o,m);
  a = o by TARSKI:def 1;
  hence thesis by TARSKI:def 1;
end;
