
theorem Th683:
Sum digits(3540,10) = 12
proof
  thus Sum digits(3540,10) = Sum <%0,4,5%>+Sum <%3%> by Th682,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%5%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%5%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 4 + 5) + Sum <%3%> by AFINSQ_2:53
  .= 9 + 3 by AFINSQ_2:53
  .= 12;
end;
