
theorem Th27:
Sum digits(60,10) = 6
proof
  thus Sum digits(60,10) = Sum <%0%>+Sum <%6%> by Th26,AFINSQ_2:55
  .= 0 + Sum <%6%> by AFINSQ_2:53
  .= 6 by AFINSQ_2:53;
end;
