
theorem Th1216:
Sum digits(2650,10) = 13
proof
  thus Sum digits(2650,10) = Sum <%0,5,6%>+Sum <%2%> by Th1215,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%6%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%6%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 5 + 6) + Sum <%2%> by AFINSQ_2:53
  .= 11 + 2 by AFINSQ_2:53
  .= 13;
end;
