
theorem Th383:
Sum digits(520,10) = 7
proof
  thus Sum digits(520,10) = Sum <%0,2%>+Sum <%5%> by Th382,AFINSQ_2:55
  .= (0 + 2) + Sum <%5%> by AFINSQ_2:54
  .= 2 + 5 by AFINSQ_2:53
  .= 7;
end;
