
theorem Th529:
Sum digits(2000,10) = 2
proof
  thus Sum digits(2000,10) = Sum <%0,0,0%>+Sum <%2%> by Th528,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%0%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%0%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 0 + 0) + Sum <%2%> by AFINSQ_2:53
  .= 2 by AFINSQ_2:53;
end;
