
theorem Th369:
Sum digits(300,10) = 3
proof
  thus Sum digits(300,10) = Sum <%0,0%>+Sum <%3%> by Th368,AFINSQ_2:55
  .= (0 + 0) + Sum <%3%> by AFINSQ_2:54
  .= 3 by AFINSQ_2:53;
end;
