
theorem Th535:
Sum digits(2060,10) = 8
proof
  thus Sum digits(2060,10) = Sum <%0,6,0%>+Sum <%2%> by Th534,AFINSQ_2:55
  .= Sum <%0,6%> + Sum <%0%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 6) + Sum <%0%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 6 + 0) + Sum <%2%> by AFINSQ_2:53
  .= 6 + 2 by AFINSQ_2:53
  .= 8;
end;
