
theorem Th134:
Sum digits(247,10) = 13
proof
  thus Sum digits(247,10) = Sum <%7,4%>+Sum <%2%> by Th133,AFINSQ_2:55
  .= (7 + 4) + Sum <%2%> by AFINSQ_2:54
  .= 11 + 2 by AFINSQ_2:53
  .= 13;
end;
