
theorem Th66:
Sum digits(66,10) = 12
proof
  thus Sum digits(66,10) = Sum <%6%>+Sum <%6%> by Th65,AFINSQ_2:55
  .= 6 + Sum <%6%> by AFINSQ_2:53
  .= 6+6 by AFINSQ_2:53
  .= 12;
end;
