
theorem Th381:
Sum digits(500,10) = 5
proof
  thus Sum digits(500,10) = Sum <%0,0%>+Sum <%5%> by Th380,AFINSQ_2:55
  .= (0 + 0) + Sum <%5%> by AFINSQ_2:54
  .= 5 by AFINSQ_2:53;
end;
