
theorem Th651:
Sum digits(3220,10) = 7
proof
  thus Sum digits(3220,10) = Sum <%0,2,2%>+Sum <%3%> by Th650,AFINSQ_2:55
  .= Sum <%0,2%> + Sum <%2%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 2) + Sum <%2%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 2 + 2) + Sum <%3%> by AFINSQ_2:53
  .= 4 + 3 by AFINSQ_2:53
  .= 7;
end;
