
theorem Th889:
Sum digits(2046,10) = 12
proof
  thus Sum digits(2046,10) = Sum <%6,4,0%>+Sum <%2%> by Th888,AFINSQ_2:55
  .= Sum <%6,4%> + Sum <%0%> + Sum <%2%> by AFINSQ_2:55
  .= (6 + 4) + Sum <%0%> + Sum <%2%> by AFINSQ_2:54
  .= (6 + 4 + 0) + Sum <%2%> by AFINSQ_2:53
  .= 10 + 2 by AFINSQ_2:53
  .= 12;
end;
