
theorem Th97:
Sum digits(36,10) = 9
proof
  thus Sum digits(36,10) = Sum <%6%>+Sum <%3%> by Th96,AFINSQ_2:55
  .= 6 + Sum <%3%> by AFINSQ_2:53
  .= 6+3 by AFINSQ_2:53
  .= 9;
end;
