theorem Th58:
  dom v = bound_QC-variables(Al) & dom (x|a) = {x}
proof
  v is Element of Funcs(bound_QC-variables(Al),A) by VALUAT_1:def 1;
  then ex f st v = f & dom f = bound_QC-variables(Al) & rng f c= A
   by FUNCT_2:def 2;
  hence dom v = bound_QC-variables(Al);
  thus thesis;
end;
