
theorem Th375:
Sum digits(440,10) = 8
proof
  thus Sum digits(440,10) = Sum <%0,4%>+Sum <%4%> by Th374,AFINSQ_2:55
  .= (0 + 4) + Sum <%4%> by AFINSQ_2:54
  .= 4 + 4 by AFINSQ_2:53
  .= 8;
end;
