
theorem Th673:
Sum digits(3440,10) = 11
proof
  thus Sum digits(3440,10) = Sum <%0,4,4%>+Sum <%3%> by Th672,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%4%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%4%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 4 + 4) + Sum <%3%> by AFINSQ_2:53
  .= 8 + 3 by AFINSQ_2:53
  .= 11;
end;
