
theorem Th64:
Sum digits(55,10) = 10
proof
  thus Sum digits(55,10) = Sum <%5%>+Sum <%5%> by Th63,AFINSQ_2:55
  .= 5 + Sum <%5%> by AFINSQ_2:53
  .= 5+5 by AFINSQ_2:53
  .= 10;
end;
