
theorem Th911:
Sum digits(2310,10) = 6
proof
  thus Sum digits(2310,10) = Sum <%0,1,3%>+Sum <%2%> by Th910,AFINSQ_2:55
  .= Sum <%0,1%> + Sum <%3%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 1) + Sum <%3%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 1 + 3) + Sum <%2%> by AFINSQ_2:53
  .= 4 + 2 by AFINSQ_2:53
  .= 6;
end;
