
theorem Th161:
Sum digits(238,10) = 13
proof
  thus Sum digits(238,10) = Sum <%8,3%>+Sum <%2%> by Th160,AFINSQ_2:55
  .= (8 + 3) + Sum <%2%> by AFINSQ_2:54
  .= 11 + 2 by AFINSQ_2:53
  .= 13;
end;
