theorem Th28:
    (canHom q)"([#](A/q)) = [#]A
    proof
      (canHom q)"([#](A/q)) = (canHom q)"(rng(canHom q))by FUNCT_2:def 3
      .= dom(canHom q) by RELAT_1:134 .= [#]A by FUNCT_2:def 1;
      hence thesis;
    end;
