
theorem Th962:
Sum digits(598,10) = 22
proof
  thus Sum digits(598,10) = Sum <%8,9%>+Sum <%5%> by Th961,AFINSQ_2:55
  .= (8 + 9) + Sum <%5%> by AFINSQ_2:54
  .= 17 + 5 by AFINSQ_2:53
  .= 22;
end;
