
theorem Th1230:
Sum digits(2875,10) = 22
proof
  thus Sum digits(2875,10) = Sum <%5,7,8%>+Sum <%2%> by Th1229,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%8%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%8%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 7 + 8) + Sum <%2%> by AFINSQ_2:53
  .= 20 + 2 by AFINSQ_2:53
  .= 22;
end;
