
theorem Th128:
Sum digits(208,10) = 10
proof
  thus Sum digits(208,10) = Sum <%8,0%>+Sum <%2%> by Th127,AFINSQ_2:55
  .= (8 + 0) + Sum <%2%> by AFINSQ_2:54
  .= 8 + 2 by AFINSQ_2:53
  .= 10;
end;
