
theorem Th17:
Sum digits(10,10) = 1
proof
  thus Sum digits(10,10) = Sum <%0%>+Sum <%1%> by Th16,AFINSQ_2:55
  .= 0 + Sum <%1%> by AFINSQ_2:53
  .= 1 by AFINSQ_2:53;
end;
