
theorem Th992:
Sum digits(989,10) = 26
proof
  thus Sum digits(989,10) = Sum <%9,8%>+Sum <%9%> by Th991,AFINSQ_2:55
  .= (9 + 8) + Sum <%9%> by AFINSQ_2:54
  .= 17 + 9 by AFINSQ_2:53
  .= 26;
end;
