
theorem Th174:
Sum digits(105,10) = 6
proof
  thus Sum digits(105,10) = Sum <%5,0%>+Sum <%1%> by Th173,AFINSQ_2:55
  .= (5 + 0) + Sum <%1%> by AFINSQ_2:54
  .= 5 + 1 by AFINSQ_2:53
  .= 6;
end;
