
theorem Th49:
Sum digits(170,10) = 8
proof
  thus Sum digits(170,10) = Sum <%0,7%>+Sum <%1%> by Th48,AFINSQ_2:55
  .= (0 + 7) + Sum <%1%> by AFINSQ_2:54
  .= 7 + 1 by AFINSQ_2:53
  .= 8;
end;
