
theorem Th469:
Sum digits(1400,10) = 5
proof
  thus Sum digits(1400,10) = Sum <%0,0,4%>+Sum <%1%> by Th468,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%4%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%4%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 0 + 4) + Sum <%1%> by AFINSQ_2:53
  .= 4 + 1 by AFINSQ_2:53
  .= 5;
end;
