
theorem Th1366:
Sum digits(4850,10) = 17
proof
  thus Sum digits(4850,10) = Sum <%0,5,8%>+Sum <%4%> by Th1365,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%8%> + Sum <%4%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%8%> + Sum <%4%> by AFINSQ_2:54
  .= (0 + 5 + 8) + Sum <%4%> by AFINSQ_2:53
  .= 13 + 4 by AFINSQ_2:53
  .= 17;
end;
