
theorem Th1368:
Sum digits(4875,10) = 24
proof
  thus Sum digits(4875,10) = Sum <%5,7,8%>+Sum <%4%> by Th1367,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%8%> + Sum <%4%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%8%> + Sum <%4%> by AFINSQ_2:54
  .= (5 + 7 + 8) + Sum <%4%> by AFINSQ_2:53
  .= 20 + 4 by AFINSQ_2:53
  .= 24;
end;
