
theorem Th978:
Sum digits(782,10) = 17
proof
  thus Sum digits(782,10) = Sum <%2,8%>+Sum <%7%> by Th977,AFINSQ_2:55
  .= (2 + 8) + Sum <%7%> by AFINSQ_2:54
  .= 10 + 7 by AFINSQ_2:53
  .= 17;
end;
