
theorem Th132:
Sum digits(234,10) = 9
proof
  thus Sum digits(234,10) = Sum <%4,3%>+Sum <%2%> by Th131,AFINSQ_2:55
  .= (4 + 3) + Sum <%2%> by AFINSQ_2:54
  .= 7 + 2 by AFINSQ_2:53
  .= 9;
end;
