
theorem Th201:
Sum digits(304,10) = 7
proof
  thus Sum digits(304,10) = Sum <%4,0%>+Sum <%3%> by Th200,AFINSQ_2:55
  .= (4 + 0) + Sum <%3%> by AFINSQ_2:54
  .= 4 + 3 by AFINSQ_2:53
  .= 7;
end;
