
theorem Th845:
Sum digits(1496,10) = 20
proof
  thus Sum digits(1496,10) = Sum <%6,9,4%>+Sum <%1%> by Th844,AFINSQ_2:55
  .= Sum <%6,9%> + Sum <%4%> + Sum <%1%> by AFINSQ_2:55
  .= (6 + 9) + Sum <%4%> + Sum <%1%> by AFINSQ_2:54
  .= (6 + 9 + 4) + Sum <%1%> by AFINSQ_2:53
  .= 19 + 1 by AFINSQ_2:53
  .= 20;
end;
