
theorem Th907:
Sum digits(2266,10) = 16
proof
  thus Sum digits(2266,10) = Sum <%6,6,2%>+Sum <%2%> by Th906,AFINSQ_2:55
  .= Sum <%6,6%> + Sum <%2%> + Sum <%2%> by AFINSQ_2:55
  .= (6 + 6) + Sum <%2%> + Sum <%2%> by AFINSQ_2:54
  .= (6 + 6 + 2) + Sum <%2%> by AFINSQ_2:53
  .= 14 + 2 by AFINSQ_2:53
  .= 16;
end;
