
theorem Th300:
Sum digits(285,10) = 15
proof
  thus Sum digits(285,10) = Sum <%5,8%>+Sum <%2%> by Th299,AFINSQ_2:55
  .= (5 + 8) + Sum <%2%> by AFINSQ_2:54
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
