
theorem Th693:
Sum digits(3640,10) = 13
proof
  thus Sum digits(3640,10) = Sum <%0,4,6%>+Sum <%3%> by Th692,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%6%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%6%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 4 + 6) + Sum <%3%> by AFINSQ_2:53
  .= 10 + 3 by AFINSQ_2:53
  .= 13;
end;
