
theorem Th33:
Sum digits(90,10) = 9
proof
  thus Sum digits(90,10) = Sum <%0%>+Sum <%9%> by Th32,AFINSQ_2:55
  .= 0 + Sum <%9%> by AFINSQ_2:53
  .= 9 by AFINSQ_2:53;
end;
